physics - mselkirk.weebly.com 3 of 28 higher level question 1. 40 marks in an experiment to...

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PRE-LEAVING CERTIFICATE EXAMINATION, 2015

MARKING SCHEME

PHYSICS

HIGHER AND ORDINARY LEVEL

*WMS13*

35 Finglas Business Park, Tolka Valley Road, Finglas, Dublin 11T: 01 808 1494, F: 01 836 2739, E: [email protected], W: www.examcraft.ie

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In considering this marking scheme the following points should be noted:

1. In many instances only key words are given, words that must appear in the correct context in the candidate’s answer in order to merit the assigned marks.

2. Words, expressions or statements separated by a solidus, /, are alternatives which are equally acceptable.

3. Answers that are separated by a double solidus, //, are answers which are mutually exclusive. A partial answer from one side of the // may not be taken in conjunction with a partial answer from the other side.

4. The descriptions, methods and defi nitions in the scheme are not exhaustive and alternative valid answers are acceptable.

5. The detail required in any answer is determined by the context and manner in which the question is asked and by the number of marks assigned to the answer in the examination paper. Therefore, in any instance, it may vary from year to year.

6. For lack of units, or incorrect units, one mark is deducted, as indicated.

7. Each time an arithmetical slip occurs in a calculation one mark is deducted.

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HIGHER LEVEL Question 1. 40 marks

In an experiment to investigate the relationship between the acceleration of a body and the force applied to it, you recorded the following data.

F(N) 0.4 0.8 1.2 1.6 2.0 2.4 2.8a(ms–2) 0.08 0.18 0.28 0.31 0.45 0.51 0.6

Describe the procedure involved in measuring the acceleration of the body.– measure/calculate the initial velocity/speed 3– measure/calculate the velocity/speed again (t seconds later ) 3– measure time interval from initial to fi nal velocities / distance between light gates 3– use relevant formula e.g. v = u + at / v2 = u2 + 2as 3

Using the data above, plot a graph showing the relationship between the acceleration of the body and the force applied to it.

y = 4,6369x + 0,0036

0

0,5

1

1,5

2

2,5

3

00 ,1 0,20 ,3 0,40 ,5 0,60 ,7

F

a

– label axes correctly on graph paper 3– plot six points correctly (– 1 per each incorrect/omitted point) 3– straight line 3– good distribution 3– correct statement / correct equation /a α F 4

From your graph, fi nd the mass of the body– correct method for slope 3 m = 4.6 kg [range: 4.5 ↔ 4.7 kg] 3 (– 1 for omission of or incorrect units)

After completing this experiment, a student found that the graph did not go through the origin. Suggest a possible reason for this and describe how the apparatus should be adjusted, so that the graph would go through the origin.– friction / any valid reason 3– elevate/adjust the track/slope 3

0,0, 0, 0,

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Question 2. 40 marks

In an experiment to measure the wavelength of a monochromatic light source, a narrow beam of light was incident normally on a diffraction grating having 400 lines per mm. A number of bright images were observed. The angles θ between the central bright image and the fi rst two images to the left and right were measured and recorded as shown below.

2nd image to the left of centre

1st image to the left of centre

Centre image 1st image to the right of centre

2nd image to the right of centre

θ ( °) 30 14 0 14.5 31

Name a source of monochromatic light– sodium (Na) lamp / laser 6

Describe, with the aid of a diagram, how the data above was obtained

– A diagram including a monochromatic light source, spectrometer, grating (on turntable) (– 1 if no diagram) 2– focus on zero image and read scale/zero the turntable 2– focus on fi rst image on LHS and read scale– focus on fi rst image on RHS and read scale – repeat for subsequent images on both sides 2

Using the data, calculate the wavelength of the monochromatic light. nλ =d sinΘ 2 d = 1/400 = 0.0025 × 10-3m 2 λ = 604 nm, 625 nm, 625 nm and 643 nm λaverage = 624 nm (– 1 for omission of or incorrect units) 2

Based on your results, what source of monochromatic light was used?– A red laser (HeNe) 6

(i) Using a monochromatic light source of longer wavelength– larger Θ / images more spaced out /any true statement 6

(ii) Increasing the distance between the slits– smaller Θ / images closer together /any true statement 6

(iii) Using a source of white light instead of monochromatic light– each fringe/image is a spectrum (of white light) // each fringe/image consists of many colours 4

Collimator

Slit

Source

Grating

Telescope

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In an experiment to measure the specifi c latent heat of vaporisation of water, a student used a copper calorimeter containing water and a sensitive thermometer. The water was cooled below room temperature before adding dry steam to it.

How was the water cooled below room temperature?– appropriate use of ice / water taken from fridge 6

How was the steam dried?– use of steam trap / delivery tube sloped upwards 6

Describe how the mass of the steam was determined– fi nal mass of calorimeter plus contents/water – initial mass of calorimeter and contents/water 6

Why was a sensitive thermometer used?– for greater accuracy / to reduce (%) error / more signifi cant fi gures / e.g. to read to 0.1 oC 6

Using the data, calculate the specifi c latent heat of vaporisation of water [heat lost by steam = heat gained by water and calorimeter] Ms = 1.2 × 10–3 kg Mw = 62 × 10–3 kg 3 Δθs = 80 Δθw = 11.8 3 (ml)s + (mcΔθ )s = (mcΔθ )w+ (mcΔθ )c 4 (1.2 × 10–3 l) + (1.2 × 10–3 × 4180 × 80) = (62 × 10–3 × 4180 × 11.8) + (34.6 × 10–3 × 390 × 11.8)

zero marks if ml component missing (1.2 × 10–3 l) + 401.28 = 3058.09 + 159.23 l = 2816.07 / 1.2 × 10–3 3 (–1 per each incorrect substitution)

l = 2.35 × 106 J kg–1 3 (–1 for omission of or incorrect units)

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The following is part of a student’s report on an experiment to investigate the variation of the current I with potential difference V for a semiconductor diode.

“I set up the apparatus as shown in the circuit diagram. I measured the current fl owing through the diode for different values of the potential difference. I recorded the following data.”

V (V) 0 0.49 0.60 0.64 0.69 0.71 0.73

I (mA) 0 3.0 5.4 11.7 17.4 27.3 36.5

Draw a circuit diagram used by the student.– apparatus: Power supply unit., ammeter, voltmeter, diode 3 (–1 per missing item)– correct arrangement 3– diode in forward bias (state/imply) 3

How did the student vary and measure the potential difference?– vary using rheostat /variable resistor / dial on (variable) power supply. 3– measure p.d. from voltmeter (across diode – stated or implied) 3

Using the data, draw a graph to show how the current varies with the potential difference for the semiconductor diode.

0

5

10

15

20

25

30

35

40

00 ,1 0,20 ,3 0, 0,40 ,5 0,60 ,7 0,8

Curren

t

Voltage0,0,0,

– label axes correctly 3– plot points (–1 per each incorrect point) 6– good distribution (–1 if not drawn from the origin) 3

Does the resistance of the diode remain constant during the investigation? Justify your answer.– no / ‘resistance not constant’ 3– I not proportional to V or equivalent, e.g. ‘graph does not follow a straight line through origin’. 3The student continued the experiment with the connections to the semiconductor diode reversed. What adjustments should be made to the circuit to obtain valid readings?Sketch the graph that the student would obtain.– microammeter used (instead of ammeter/milliammeter) // voltmeter placed across diode and microammeter, etc 3– Correct sketch showing much smaller current eventually leading to breakdown 4

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SECTION B (280 marks)

Answer fi ve questions from this section. Each question carries 56 marks. Question 5. 56 marks

(a) What are the two conditions for the equilibrium of a set of co-planar forces? forces up = forces down // (algebraic) sum of forces acting is zero 4 (algebraic) sum of the moments (of the forces about any point) is zero 3

(b) What is the critical angle of a sample of glass whose refractive index is 1.5? n = 1 / sin ic 4 ic = 41.8º 3

(c) Name the parts labelled A and B of the spectrometer shown in the diagram. A = turntable, B = telescope 4 + 3

(d) Explain why snow is slow to melt as the air temperature rises above 0 °C. latent heat (of snow/ice) / energy needed for change of state 4 is (very) large 3

(e) What is the positive charge stored on a 10 μF capacitor when it is connected to a 120 V d.c. supply? q = C V 4 q = 1.2 × 10–3 C / 1.2 mC (–1 for omission of or incorrect units) 3 (f) Name the two optical phenomena that occur when white light passes through a prism. Dispersion 4 Diffraction 3

(g) When will an RCD (residual current device) disconnect a circuit? If there is a leakage current (when magnitude of the) current fl owing in differs // leakage of current 4 from that fl owing out // to earth (ground) 3

(h) The peak voltage of an a.c. supply is 300 V. Calculate its rms voltage. rms = a/√2 212 V (–1 for omission of or incorrect units) 4+3

(i) Draw a ray diagram to show the formation of an image in a convex mirror.

two correct refl ected rays 4 image behind the mirror 3

Image

F

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(j) Give two advantages of a circular accelerator over a linear accelerator. Particles in a circular accelerators go around many times, getting multiple kicks of energy each time around the fact that the particles go around many times means that there are many chances for collisions at those places where particle beams are made to cross. 4 + 3

or

Draw the truth table for the AND gate.

A B out0 0 00 1 01 0 01 1 1

4 for partially correct, 7 for fully correct


Calculate the acceleration due to gravity at a height of 39 km above the surface of the earth. g = GM/d2 6 g = (6.7 × 10–11) × (5.97 × 1024)/ (6.399 × 106)2 6 g = 9.77 ms–2 (–1 for omission of or incorrect units) 2

What was the downward force exerted on Felix and his equipment at 39 km, taking their total mass to be 200 kg? (W = F =) mg 4 F = 200(9.77) / 1954 N (–1 for omission of or incorrect units) 4

Estimate how far he fell during the fi rst 10 seconds. s = ut + ½ at2 3 s = 0 + ½ (9.77) 102 3 s = 488.5 m (–1 for omission of or incorrect units) 3

What assumptions did you take in this calculation? u taken as zero / g constant / no atmospheric resistance / any two 3+2

What was his average speed during the remaining 9 minutes and 50 seconds? average speed = distance ÷ time 4 distance = 39000 – 488.5 = 38511.5 m 4 average speed = 38511.5/590 = 65.27 ms–1 (–1 for omission of or incorrect units) 3

Calculate the upthrust that acted on Felix when he reached constant velocity in the last stage of his descent (assume g = 9.81 m s–2 during this stage). upthrust (U) = mg 3 = (200)(9.81) 3 = 1962 N (–1 for omission of or incorrect units) 3

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State Newton’s second law of motion. – force is proportional to the 3– rate of change of momentum 3 or (F = ma 3 explain symbols 3)

The equation F = – ks, where k is a constant, describes a law that governs the motion of a body. Name this law and give its defi nition. – Hooke’s Law 3– restoring force ∝ (= to k times) // Extension ∝ 3– displacement // force / load / weight 3

Give the name for this type of motion and describe the motion. – simple harmonic motion / SHM 3– a = −ω2s // acceleration is α to 3– explain // displacement / distance (and direction) 3

A mass at the end of a spring is an example of a system that obeys this law. Give two other examples of systems that obey this law. stretched elastic / pendulum, oscillating magnet, springs of car, vibrating tuning fork, object bobbing in water waves, ball in saucer, etc . or any system that obeys Hook’s law. any two 3+3

The springs of a mountain bike are compressed vertically by 5 mm when a cyclist of mass 80 kg sits on it. When the cyclist rides the bike over a bump on a track, the frame of the bike and the cyclist oscillate up and down.Using the formula F = – ks, calculate the value of k, the constant for the springs of the bike. F = mg /80 × 9.8 / 784 (N) 3 1.57×105 N m-1 3 (–1 for lack of units or incorrect units)

The total mass of the frame of the bike and the cyclist is 100 kg.

Calculate

(i) the period of oscillation of the cyclist, k/m = ω2 4 ω = 40 s–1 3 T = 2π/ ω 3 = 0.157s (accept 0.15 – 0.16s) 3

(ii) the number of oscillations of the cyclist per second. f = 1/T 4 =1/0.157 = 6.4 (accept 6 – 6.5) 3

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(a) A straight wire carrying a current is surrounded by a magnetic fi eld. How can this magnetic fi eld be detected? – compass / iron fi lings any one 4

Sketch the shape of this magnetic fi eld.– rings around the wire 4– arrows indicating direction of magnetic fi eld 4

Name one other effect of an electric current.– heating / chemical any one 2

The fi gure shows a circuit with a 10 Ω resistor and a 5 Ω resistor in series connected to a battery. The current in the circuit is 0.4 A.

(i) the effective resistance of the two resistors R = R1 + R2 / R = 10 + 5 4 15 Ω 3 (ii) the voltage (potential difference) across the 5 Ω resistor. V = R × I / V = (5)(0.4) 4 2 V 3

(b) State Coulomb’s law of forces between electric charges. – force proportional to product of charges // F = Q1Q2/4πεr

2 // F ∝ Q1Q2/r2 3

– inversely proportional to square of distance // explain notation // explain notation 3

Defi ne electric fi eld strength and state the unit in which it is measured. E = F/Q // force per unit charge 3 Newton/Coulomb or N/C 3

Use Coulomb’s law to derive an expression for the electric fi eld strength at a distance r from a point charge Q. F = kQ1Q2/r

2 = EQ 4 E = kQ/r2 5

Calculate the magnitude of the electric fi eld strength at a point which is 5 cm from a positive charge of 2 μC. E = Q/4πε r2 E = 2 × 10–6 / (4 × 3.14 × 9 × 10–12) × (5 × 10–2)2 4 E = 7.1 × 106 NC–1 (–1 for omission of or incorrect units) 3

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What is thermionic emission?– the emission of electrons 3– (from the) surface of a hot metal 3

X-rays are produced when high-energy electrons collide with a target. Draw a labelled diagram of an X-ray tube.

– vacuum 3– cathode 3– target / anode 3– high (accelerating anode) voltage or H.T. / shielding / cooling / low (cathode) voltage or L.T. 3

What are X-rays and how do they differ from light rays?– what: electromagnetic radiation / photons / quanta of energy 6– high frequency / short wavelength / high energy 3– how: x-rays penetrate matter / cause ionization / any valid property 3

Give two uses of X-rays.– (medical) analysis of bone structure/ luggage scanners (at airports) / any specifi c medical, industrial or security use, etc. any two 2×3

When electrons hit the target in an X-ray tube, only a small percentage of their energy is converted into X-rays. What happens to the rest of their energy and how does this infl uence the type of target used?– Their energy is converted to heat 6– This means the target material must have a very high melting, eg tungsten 3

A potential difference (voltage) of 55 kV is applied across an X-ray tube. Calculate:

(i) the maximum energy of an electron as it hits the target 1/2mv2 max = eV 3 = 1.6 x10−19 × 55000 = 8.8 × 10−15 J (–1 for omission of or incorrect units) 3

(ii) the frequency of the most energetic X-ray produced. E=hf ⇒ f =E/h 3 =8.8 × 10−15 / 6.6 × 10−34 = 1.3 × 1019 Hz (–1 for omission of or incorrect units) 2

Tungsten Anode Electron Beam

Cathode

Cathode ArmAnode Arm

X-Ray Beam

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(a) In 1932 the English physicist, John Cockroft and the Irish physicist, Ernest Walton, bombarded lithium with protons. How were the protons accelerated? How were the alpha particles detected?– high voltage 4– scintillations / fl ashes of light / zinc sulphide (or phosphor) screen 4

Write a nuclear equation to represent the splitting of a lithium nucleus by a proton. 3

7Li + 11H 2

4He + 24He 4 × 3

(1 mark per each correct component)

Calculate the energy released in this reaction. loss in mass = (1.33186× 10–26) – (1.32894 × 10–26) / 2.92 × 10–29 3 E = mc2 3 E = (2.92 × 10–29)(2.9979 × 108)2 J / 2.6 × 10–12 J 3 (–1 for omission of or incorrect unit)

Most of the accelerated protons did not split a lithium nucleus. Explain why.– atom is mostly empty space 3– protons did not collide with lithium nucleus / passed straight through 3

Explain why new particles are formed.– kinetic energy of protons // energy converted 3– changed into mass // into mass 3

What is the maximum net mass of the new particles created per collision? total energy = 4 GeV 3 E = mc2

m = E/c2 = 4 × 109 × 1.6 × 10-19 / (3 × 108)2 3 m = 7.11 × 1027 kg (–1 for omission of or incorrect unit) 3 What is the advantage of using circular particle accelerators in particle physics? They are more compact and can accelerate particles to higher energies. 6

(b) State the principle of operation of an electric motor.– a current-carrying conductor in a magnetic fi eld // a current-carrying coil in a magnetic fi eld 3 – experiences a force // experiences a torque/turning moment 3

Name each of the parts labelled A and B on the diagram and state the function of each. A – a split ring commutator 3 B – a brush 3 Function: A – to ensure that coil rotates in the same direction (continuously) B – to allow current fl ow from battery into coil as it rotates (both functions correct) 3

What material is normally used in part B? Give two properties of this material that make it suitable for use in a motor. – carbon / graphite 3– lubricant, soft, conductor, etc. any two 2 + 1

List three factors that affect the torque (couple) acting on the coil.– magnetic fl ux density (B) , size of current (I), number of turns (N), area of coil (A) 3 × 1

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If the motor jammed, a larger current than normal would fl ow through the motor. Explain why.– no back/opposing emf (induced) 6

What would be the effect on the motor if this happened?– motor would burn out / overheat 6

What changes can be made to a d.c. motor to convert it to an a.c. generator?– (split ring commutator) replaced by slip rings 3 – attach handle to rotate coil 3

Draw a sketch of the output voltage from an a.c. generator.

Label axis 3 Correct shape 6

Give two ways in which the output voltage from an a.c. generator can be increased. rotate handle faster / more turns of wire / more powerful magnet (any two) 3 + 2


(a) What is meant by a photon of light?– a photon is a discrete bundle (or quantum) 2– of electromagnetic /light energy 2

(b) What is the photoelectric effect?– The photoelectric effect is the emission of electrons from a material 2– upon the absorption of electromagnetic radiation of suitable wavelength 2

(c) Explain with the aid of a diagram how X-Ray production is the inverse of the photoelec tric effect In the photoelectric effect electrons are emitted from the surface of a metal when suffi ciently energetic photons strike it. In X-ray production high-energy electrons strike a metal and cause the emission of photons. 3 Suitable diagram showing x-ray production and photoelectric effect 3

(d) Give an expression for Einstein’s photoelectric law. Partly correct 4, fully correct 6

(e) What is the threshold frequency of the light? 4 × 1014 Hz 6

Time

+V

0V

–V

An AC Waveform

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(f) What is the energy of the light shining when the frequency is the threshold frequency? E = hf 3 E = 6.63 × 10–34 Js × 4 × 1014

= 2.7 × 10–19 J 3

(g) What is the work function of the metal? hf0 = φ 3 = 2.7 × 10–19 J (–1 for omission of or incorrect units) 3

(h) What is the frequency of light shining on the metal when the wavelength of the light is 550 nm f = c/λ 3 = 3 × 108 / 550 × 10–9 = 5.5 × 1014 Hz (–1 for omission of or incorrect units) 3

(i) What is the maximum energy of an emitted electron when light of wavelength 550 nm shines on it? What type of energy is this? =3.65 × 10–19 – 2.7 × 10–19 2 = 0.95 × 10–19 J (–1 for omission of or incorrect units) 2 This falls into the infrared energy range 2

(j) Explain why current does NOT fl ow when the frequency of light is less than 4 × 1014Hz frequency less than 3 threshold frequency 3


(a) Defi ne capacitance. Capacitance is the ability of a body to store an electrical charge //the ratio of the change in an electric charge in a system to the corresponding change in its electric potential 3 + 3 Mention two common uses of capacitors A capacitor can store electric energy so it can be used like a temporary battery, old camera fl ashes, motor starters, tuning circuits eg, radios`… 3 + 3 A parallel plate capacitor has two square plates of side 12 cm, which are 3 mm apart. Calculate the capacitance of the capacitor and calculate the energy stored in the capacitor when the potential difference between the plates is 180 V. C = kε0A/d 4 = 1 × 9 × 10–12 × 0.0144 / 3 × 10–3

= 4.3 × 10–11 F 4 E = ½ CV2 4 = ½ 4.3 × 10–11 × 1802

= 6.99 × 10–7 J (–1 for omission of or incorrect unit) 4

(b) List the instructions you should give the student so that the data-logger will display the graph shown in the fi gure below. Stand 2m from sensor for 2s, move 1m away in 1 s, stand still for 1.5 s, return to starting position in 1.5 s. Partially correct 2, fully correct 4 How many different velocities can you see? 3 (zero velocity occurs twice) 5 What is the total of all the velocities added together? Zero (velocity is a vector and as you return to starting position the sum must be zero) 5

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Using the graph, calculate the distance travelled by the cyclist and the average speed for the journey. Distance = area under the graph 4 Convert to similar units, ie 5 s = 1/12 h 2 Area 1 = ½ × 1/12 × 15 = 0.625 km Area 2 = 2/12 × 15 = 2.5 km Area 3 = ½ × 1/12 × 15 = 0.625 km Total = 3.75 km (–1 for omission of or incorrect units) 1 Average speed = distance/time = 3750m / (1200s) 4 = 3.1 ms-1 3

(c) What is radioactivity?– the process by which a nucleus of an unstable atom loses energy 3– by emitting ionizing radiation 3 Which type of nuclear radiation emits positively charged particles?– alpha particles are positively charged 6 List two uses of radioactive substances– sterilise instruments and food, produce energy for heat and electric power, medical use… any 2 valid uses 4 + 4

Give two precautions when using radioactive substances– Alpha and beta emitters can be handled using thick gloves, Gamma ray emitters must be handled only by remote control– Radioactive materials must be stored in thick lead containers– People working with radioactive isotopes must wear protective clothing with dosimeter... 2 valid reasons 4 + 4

(d) Defi ne magnetic fl ux– It is a measure of the amount of magnetic fi eld 3 – passing through a given surface 3 State Faraday’s law of electromagnetic induction– The law states whenever a conductor is rotated in magnetic fi eld, an emf is induced 3– The induced emf is equal to the rate of change of fl ux 3 A square coil of side 5 cm lies perpendicular to a magnetic fi eld of fl ux density 5T. The coil consists of 300 turns of wire. What is the magnetic fl ux cutting the coil? Φ = BA cos θ 4 = 5 (5 × 10–2)2 Cos( 0) = 0.0125 Wb (–1 for omission of or incorrect units) 4 The coil is rotated through an angle of 90o in 0.4 seconds. Calculate the magnitude of the average e.m.f. induced in the coil while it is being rotated. emf = – N φ / t 4 =300 × 0.0125/0.4 2 = 9.375 V (–1 for omission of or incorrect units)

2

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ORDINARY LEVELQuestion 1. 40 marks

(i) Draw a labelled diagram of the apparatus you used. (3 × 3) Labelled diagram to show: – trolley / rider – runway / air-track – means of applying a force e.g. string over pulley to weight on pan – means of measuring acceleration e.g. 2 photo-gates (and timer) // tickertape (and timer) 3 correct 3 × 3 NOTE: no labels, deduct 2 accept valid alternatives e.g. data logging methods which fi t the scheme

(ii) How did you measure the applied force? (6 or 3)– weighed the mass (and pan) / mg // from the (digital Newton) balance 6 partial answer (3)

(iii) How did you minimise the effect of friction during the experiment? (6 or 3)– slant/clean the runway // oil (the trolley) wheels / frictionless wheels 6 partial answer (3)

(iv) Plot a graph on graph paper of the body’s acceleration against the force applied to it. (3 × 2)– label axis correctly: name/symbol/unit acceptable 2– plot at least four points correctly 2– straight line 2– if graph paper is not used maximum mark (4)

(v) Using the graph, determine the mass of the body used in this experiment. (3 × 2)– use of two data points 2– correct formula 2 m = 2 kg (1.9 – 2.1) 2– if graph is not used maximum mark (2)

(vi) What does your graph tell you about the relationship between the acceleration of the body and the force applied to it? (7 or 4)– (they are ) proportional / / straight line through the origin 7– partial answer e.g. any reference to proportional (4)

y = 2x

0

0,2

0,4

0,6

0,8

1

1,2

1,4

00 ,2 0,40 ,6 0,8

Series1

Linear (Series1)

0,0,

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You carried out an experiment to measure the wavelength of a monochromatic light sourceusing a diffraction grating. The diffraction grating had 400 lines per mm.(i) Draw a labelled diagram of the apparatus that you used. (6) + (2 × 3)– diffraction grating / Young’s slits 6 (monochromatic) light source / sodium spectrometer // screen scale // metre stick any two 2 × 3 any one (3) no labels, deduct (2)

(ii) Name a source of monochromatic light (4)– sodium (lamp) / laser/ other valid answer 4

(iii) State the measurements you took during the experiment. (2 × 3)– correct angle // distance from grating to screen 3 – another correct angle // distance between fringes 3 partial answer e.g. spectrometer adjustment // laser adjustment (3)

(iv) What is the distance between each line on the diffraction grating? (6 or 3) d = 1/number of lines per metre = 1/ 400,000 = 2.5 × 10–6 m 6 partial answer e.g. correct equation (3)

(v) How did you determine the wavelength of the light? (6 or 3) nλ = d sin θ 6 partial answer (3)

(vi) Give one precaution that you took to get an accurate result (6 or 3) any one 6

eg: ensure that the crosshairs are on the centre of the fringe, level the table, focus the telescope (for infi nity), measure the angle between the fi rst order images on the left and on the right, adjust the collimator, ensure that the diffraction grating is perpendicular to the (monochromatic) light, use a grating with a large number of lines, ensure D is large, repeat for different orders and take the average, etc.partial answer e.g. repeat the experiment, mentions no parallax, refers to dark room (3)

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You carried out an experiment to measure the focal length of a converging lens.

(i) Draw a labelled diagram of the apparatus that you used in the experiment (6) + (2 × 3)– converging lens 6 object e.g. pin, raybox, crosswires, slit, bulb (fi lament) screen // pin for no parallax metre stick any two lines 2 × 3

(ii) Describe how you found the position of the image formed by the lens (2 × 3)– moved the screen/object /lens 3 – until there was a clear image // no parallax 3 partial answer (3)

(iii) What measurements did you take? (6 + 3)– distance from object to the lens // u – distance from the screen/ image to the lens // v– two correct 6 + 3 any one (6)

(iv) Using the formula 1/f = 1/u+1/v or otherwise and the above data, fi nd an average value for the focal length f of the lens.– 15.23, 17.67, 20.25, 20.59, 15 cm 5 × 2– Correct answer 17 – 18 cm 3 partial answer e.g. correct equation with a single calculation (3)

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(i) Draw a labelled diagram of the apparatus used in the experiment 2 (2 × 3)– ammeter/multimeter, heating coil, thermometer, calorimeter, insulation, stop watch any one (3) any two 2 × 3– variable power supply // power supply and variable resistance 3– detail e.g. closed circuit 3

(ii) How was the current changed during the experiment? (4) adjust the (variable) power supply // adjust the (variable) resistor 4

(iii) Copy the table and complete it in your answer book. (2 × 3)

I2 (A2) 1.0 2.25 4 6.25 9 12.25 16.0

all correct 2 × 3 any 3 correct (3)

(iv) Using the data in the completed table, draw a graph on graph paper of Δθ against I2 . Put I2 on the horizontal axis (X-axis) (4 × 3)– label axes correctly, (name / symbol / unit acceptable) 3– plot three points correctly 3– plot another three points correctly 3– straight line 3– if graph paper is not used, maximum mark (3 × 3)– if I2 is on the Y-axis, maximum mark (3 × 3)

(v) Explain how your graph verifi es Joule’s law (Δθ α I2) (2 × 3)– (straight) line 3– through origin // shows that Δθ α I2 3

y = 2,1872x + 0,0711

0

5

10

15

20

25

30

35

40

05 10 15 20

/°C

I 2 / A2

Series1

Linear (Series1)

05

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SECTION B (280 Marks)Five questions to be answered

Question 5. any eight parts 56 marks

(a) A horse gallops at a constant speed of 10 m s–1. Calculate the distance travelled by the horse in 2 minutes. (7 or 4) v = s ÷ t / 10 = s ÷ (2 × 60) / s = 1200 m 7 partial answer (4)

(b) State Newton’s second law of motion (7 or 4) rate of change of momentum is directly proportional to the applied force // F = ma 7 partial answer (4)

(c) State Boyle’s law. (7 or 4) The pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies, provided the temperature and amount of gas remain fi xed. 7 partial answer (4)

(d) What is the purpose of a fuse in this plug? (7 or 4) On overload, the wire forming the fuse element will heat up and melt (or blow) and interrupt the current fl ow thus preventing damage. 7 partial answer (4)

(e) Name one device that uses a transformer. 7 Any valid device eg, most electronic devices 7

(f) Name the electrical component represented in the diagram. 7 A photoresistor or light-dependent resistor (LDR) or photocell 7

(g) What is meant by the half-life of a radioactive substance? (7 or 4) The time it takes for a given amount of the substance to become reduced by half as a consequence of decay, and therefore, the emission of radiation. 7 partial answer (4)

(h) The half-life of a radioactive element is 3 days. What fraction of a sample of the radioactive element will remain after 9 days? (7 or 4) It reduces by a half every 3 days so ½ × ½ × ½ = 1/8 7 partial answer (4)

(i) Name the type of nuclear reaction that occurs in the Sun. 7 nuclear fusion 7

(j) In semiconductors, what is meant by doping? (7 or 4) In semiconductor production, doping intentionally introduces impurities into an extremely pure semiconductor 7 partial answer (4)

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Defi ne (i) velocity, (ii) acceleration 2 × (2 × 3)

(i) velocity: rate of change // distance ÷ time / speed 3 (of) displacement // in particular direction 3 v = s/t (2 × 3) correct unit (3)

(ii) acceleration: rate of change // change in velocity / speed 3 of velocity/speed // per second 3 a = (v – u)/t (2 × 3) correct unit (3)

Describe an experiment to measure the acceleration due to gravity, g. (18) Method: falling object/ball // pendulum bob // picket fence 3 timer: timer shown in diagram // stop-watch // photogate (and timer) 3 stop/start mechanism/ detail // fi xed point / split cork // calculator/computer 3

all valid methods are acceptable e.g. data logging methods, which fi t the scheme Measure: measure length // time // time (n) oscillations // start program / datagate 3 metre stick // timer // timing device // drop picket fence 3 Determine g: Reference substitution into the equation 3

A stone is t hrown straight up from the ground with an initial speed of 25 m s–1. Calculate the height reached after 2 s. Use the equation (s = ut + ½ a t2). (5) s = 25(2) + ½(–9.8)(2)2 2 s = 50 – 19.6 2 s = 30.4 m 1

Describe how the speed of the stone changes as it rises to its highest point. (6) slows / stops 6

Calculate the time it takes the stone to reach its highest point. Use the equation (v = u + at). (9) v = u + at 0 = 25 – 9.8t 3 t = 25/9.8 3 t = 2.6 s 3

How long will it take the stone to return to the ground? (3) Twice as long, ie 2 × (2.6) = 5.2 s 3

At what height will the stone’s kinetic energy be equal to its potential energy? (3) At half its maximum height (or by calculation 32 m) 3

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“When a wave meets an object, diffraction occurs. A wave with the correct frequency can also cause resonance in an object.” Explain the underlined terms. (3 × 6) Diffraction is the slight bending of light as it passes around the edge of an object 6 Frequency is the number of oscillations of a wave per unit time 6 Resonance is the response of a body to vibrations of its own natural frequency 6

How would you demonstrate diffraction in the laboratory? (8) Any valid method, e.g. ripple tank 8 No diagram (maximum 6)

The pitch of a note emitted by a siren of a fast moving police car appears to change as it passes a stationary observer.

(i) Name this phenomenon. (6) The Doppler effect 6

(ii) Explain how this phenomenon occurs. (6 or 4)When the source of the waves is moving toward the observer, each successive wave is emitted from a position closer to the observer than the previous wave. Therefore, each wave takes slightly less time to reach the observer than the previous wave. Hence, the time between the arrival of successive waves at the observer is reduced, causing an increase in the frequency. Conversely, if the source of waves is moving away from the observer, each wave is emitted from a position farther from the observer than the previous wave, so the arrival time between successive waves is increased, reducing the frequency. 6partial answer (4)

(iii) Give an application of this phenomenon. (6) Any valid application e.g. astronomy, radar, medical imaging, 6

If you are standing a few hundred metres from a fi reworks display, you will often see the fl ash of light from an exploding fi rework before you hear the sound of the explosion. What does this tell you about the speed of sound in air? (6 or 4) Sound travels slower than light in air 6 partial answer (4)

Name a medium in which sound travels faster than it does in air. (6) Liquids or solids 6

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(i) What is heat? (6) (form of) energy 2 × 3 partial answer e.g. work (3)

(ii) Explain how heat is transferred in a solid. (9 or 6) atoms are touching / in contact 3 (heat/energy transferred from) one to the other 3 by vibration / without the atoms moving along 3 mentions conduction / without the movement of matter / warmer to cooler (2 × 3) partial answer (3)

(iii) Describe an experiment to compare the rates of heat transfer through different solids. (12) apparatus: bath of water containing different rods which protrude at the same height // four different metals bars arranged like spokes and touch in the middle 3 melt candle wax onto the outer end of each rod/metal and stick a matchstick/pin into the candle wax 3 procedure: heat the water-bath // heat the metals over a Bunsen 3 observation // conclusion: heat is conducted along the rods and the matchsticks fall off at different times // heat is transferred at different rates 3 partial answer (3) accept all valid alternatives

(iv) Explain the term U-value. (6) U-Value is the rate of heat transfer or heat loss through a material. The lower the U-Value, the less heat loss and the more effi cient a material is. 6 partial answer e.g. insulation (4)

(v) Give an example of a thermometric property (6) e.m.f. of a thermocouple. • pressure of a gas at constant volume. • volume of a gas at constant pressure. • resistance etc. 6

(vi) Calculate the amount of energy required to raise the temperature of the water from 15 ºC to 100 ºC. (9) Δθ = 85 3 Q = (1.5)(4180)(85) 3 Q =532 950 (J) 3

(vii) The kettle takes 4 minutes to heat the water from 15 ºC to 100 ºC. Calculate the power of the kettle. (Assume all the energy supplied is used to heat the water.) (8) P = W/t = (532 950 ) ÷ (4 × 60) 4 2221 ± 1 (W) 4

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“The capacitance of a parallel plate capacitor depends on the distance between the plates.”

(i) What is a capacitor? (6) Device for storing small quantities of charge 6 partial answer e.g. insulation (4)

(ii) Describe an experiment to investigate the above statement. (18) Apparatus: capacitor meter / gold leaf electroscope / multimeter 6 Circuit / charge plates 3 Measure C / relate C to gold leaf movement 3 Vary separation between plates and repeat a number of times 3 Observation / conclusion 3

(iii) Name another factor that affects the capacitance of a parallel plate capacitor. (6) Common area of plates // permittivity of dielectric // dielectric // medium 6

(iv) Mention two common uses of capacitors. (4 + 4) Any valid use e.g. energy storage, signal fi lter, motor starter… 4 + 4

A voltage supply of 20 V is connected across the capacitor in the fi gure above.

(v) What is the charge on the plates of the capacitor? Use the formula Q = CV. (9) C = 10 × 10–6 F 3 Q = 10 × 10–6 × 20 3 Q = 2 × 10–4 (C) 3

(vi) What is the energy stored in the capacitor? Use the formula E = ½ CV2. (9) E = ½ × (10 × 10–6) × 202 6 E = 2 mJ 3

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Alpha, beta and gamma (α, β, γ) are three types of radiation.

(i) Which type is a short-wavelength electromagnetic radiation? (3) γ 3

(ii) Which type is a particle consisting of two protons and two neutrons? (3) α 3

(iii) Which type is a fast moving electron? (3) β 3

(iv) How would you detect radiation? (6) Any valid method, e.g. Geiger Counter, with Geiger-Mueller (GM) Tube or Probe, Portable Multichannel Analyser, Ionisation (Ion) Chamber, Radon Detectors 6

Nuclear fi ssion occurs in a nuclear reactor.

(v) What is nuclear fi ssion? (6) A nuclear reaction in which a heavy nucleus splits spontaneously or on impact with another particle, with the release of energy. 6 partial answer (4)

(vi) What is the role of neutrons in nuclear fi ssion? (6) In a fi ssion chain reaction, the split atom generates more neutrons as it splits. These neutrons go on to split more atoms in a chain reaction. 6 partial answer (4)

(vii) Name a fuel used in a nuclear reactor. (6) Any valid fuel eg, tritium, uranium, plutonium etc. 6

(viii) In a nuclear reactor, how can the fi ssion be controlled or stopped? (6) correct reference to (control/boron) rods // refers to slowing down neutrons 6 partial answer (3)

(ix) How is the energy produced in a nuclear reactor used to generate electricity? (9) (energy produced) converted to heat / (this is used to) generate(s) steam 6 (which) drives generator / turbine 3 partial answer (3)

(x) Give one advantage and one disadvantage of a nuclear reactor as a source of energy. (8) advantage: abundant fuel / cheap fuel / no greenhouse gases / no global warming, etc. disadvantage: risk of nuclear contamination / fallout / diffi culty of dealing with waste / dangerous, etc. advantage and disadvantage for fi ssion or fusion reactor both correct 8 advantage and disadvantage one correct (4)

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(a) The solar-powered drones absorb solar energy and turn it into electricity. The solar energy available at 20,000 m is 4 times more than that available on the earth’s surface. What causes this difference? (7) Absorption//refl ection by clouds/water vapour or dust in atmosphere 7

(b) What is a geostationary satellite? (7 or 4) A geostationary satellite is an earth-orbiting satellite, placed directly over the equator, that revolves in the same direction the earth rotates (west to east) with the same period of 24 hours 7 partial answer (4)

(c) Give an application of a geostationary satellite. (7) Geostationary satellites are used for weather forecasting, satellite TV, GPS etc 7

(d) The letter K represents a factor of one thousand, e.g. 1 km = 1000 m. What does the letter M represent? (7) M = mega // a factor of one million //1,000,000 7

(e) What is Mbps short for? (7 or 4) megabits per second 7 partial answer (4)

(f) If the average Internet speed in Ireland is 50 Mbps, how long will it take to download a 4 Mb picture? (7 or 4) 1 byte contains 8 bits 1 Mbyte = 8,000,000 bits 4 Mb = 32,000,000 bits = 32 Mbits Download speed of 50 Mbits per second, therefore t = 1/(50/32) = 0.64 seconds 7 partial answer eg reference to difference between bits and bytes (4)

(g) If a balloon is at an altitude of 20,000 m and travels around the world in 25 days, how fast was it travelling? (7 or 4) Travelling in a circle with a radius of 6,371,000 + 20,000 = 6,391,000 m Circumference = 2πr = 40,135,480 m v = d/t = 40,135,480/(25 × 24 × 60 × 60) = 19 ms–1 7 partial answer (4)

(h) If the balloon stayed aloft for 100 days, how many times would it travel around the world? (7) 100/25 = 4 times 7

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Question 12. Answer any two parts 2 × 28

(a) The diagram shows a U-shaped magnet. Copy the diagram and show on it, the magnetic fi eld lines due to the magnet. (6) diagram shows at least two lines between poles 3 direction from N to S 3

Describe an experiment to demonstrate that a current-carrying conductor in a magnetic fi eld experiences a force. (12) apparatus: power supply and conductor 3 magnetic fi eld 3 procedure: turn on power supply/current 3 observation: conductor moves/defl ects 3

List two factors that affect the size of the force on the conductor. (6) strength of magnetic fi eld/B size of current fl owing/I length of conductor in magnetic fi eld/l angle between conductor and magnetic fi eld medium any two 2 3

Name one device that is based on the principle that a current-carrying conductor in a magnetic fi eld experiences a force. (4) motor, (moving coil) meter, loudspeaker, named device which contains motor e.g. electric shaver 4

(b) State the laws of refl ection of light. (12) incident ray, normal, refl ected ray 3 on the same plane 3 angle of incidence … 3 equals the angle of refl ection 3 [incidence ray = refl ected ray 3]

When you look at a plane mirror you see a virtual image. Explain the underlined terms. (6) A plane mirror is fl at / not curved / 2 d 3 Virtual image: cannot be formed on a screen / rays appear to meet / erect / formed behind the mirror etc. any one … 3

Give one other property of the image in a plane mirror. (4) same size / laterally inverted / erect / u = v etc. any one 4

The diagram shows stage lighting similar to that found in most theatres. Only red, green and blue lights are needed to create most lighting effects. Explain why. (6) all colours can be made by mixing red, green and blue // primary colours 6 partial answer e.g. incomplete answer (3)

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(c) Describe, with the aid of a diagram, an experiment to show that a force exists between electric charges. (12) A balloon is charged by rubbing it with hair. It is then brought near some bits of paper. The charged balloon attracts the paper bits, lifting them up off the table. This demonstrates the attraction between charged objects and neutral objects. Any correct diagram 6 Correct explanation 6 partial answer (3)

What is meant by point discharge? (6) The electric fi eld strength is greater around a pointed object. 3 The intense electric fi elds surrounding a pointed object serve to ionize the surrounding air, thus enhancing its conductive ability. 3

A lightning conductor is made from a thick copper strip. One end is pointed and the other end is put into the ground. Explain how a lightning conductor protects a building from being damaged by lightning. (10) During electrical storms, huge amounts of electric charge are separated in clouds. Charges near the bottom of clouds induce equally large charges in the earth beneath, on trees and on buildings. 5 When the accumulated voltage is high enough, a discharge occurs, either within the cloud or between the cloud and the earth. A lightning conductor is usually made of thick copper and is buried deeply in the earth as this provides a low resistance path for any fl ow of electric charge between the earth and the atmosphere. 5

(d) A p-n junction (diode) is formed by doping adjacent layers of a semiconductor. A depletion layer is formed at their junction.

(i) Explain the underlined terms. (9) doping: addition of impurity (to semiconductor) / changes its conductivity semiconductor: material with (resistivity) between that of conductors and insulators two correct 6 + 3 one correct (6) partial answer; e.g. p-type / n-type (3)

(ii) How is a depletion layer formed? (6) holes and electrons recombine 6 partial answer; e.g. reference to holes and electrons (3)

The diagram shows two diodes connected to two bulbs A and B, a 6 V supply and a switch.

(iii) What is observed when the switch is closed? (6) diode A lights // B does not light 6 partial answer (3)

(iv) Explain why this happens. (7) A is forward biased // B is reverse biased // depletion layer removed in A 7 depletion layer increases in B partial answer (4)

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