FIZIKMOZAC 2010

CHAPTER 5: LIGHTANSWER

5.1 REFLECTION

1. Question 1: Johor 09(a) Converge at a point F.(b) any point at the principal axis in

front of the mirror.

(c) Real, inverted and diminished.

2.(a) Reflection(b) 15 cm(c) 2f = 30 cm

Image same size with object.(d)Objectdistance , u/cm

ImageCharacteristics

10 Virtual, upright,magnified

20 Real, inverted,magnified

30 Real, inverted, samesize as the object

40 Real, inverted,diminished

(e)

(b) any point at the principal axis in

(c) Real, inverted and diminished.

Image same size with object.

ImageCharacteristics

Virtual, upright,

Real, inverted,

Real, inverted, samesize as the objectReal, inverted,

3. Question 2: N9 08(a) Convex mirror(b) Convex mirror has a wider view

than a plane mirror.(c)(i)

Draw two incident rays andeach of them reflected at thecorrect path.Shows image formed behindthe mirror and the position infront of F.

(c)(ii)

Virtual ,upright and diminished.(any of two combination

4. Question 3: Kedah 07(a) Convex mirror(b) Upright / diminished / smaller /

virtual(c) A radial ray that is incident

through the centre ofcurvature, C of the curvedmirroris reflected back along theincident path through point CDetermine the correct positionof the image

(d) To increase the field of vision

5. Question 6: SBP final F4 07(a) Image that cannot be formed on

screen(b)(i)

Image in Diagram 6.1 is bigger//vice versa

(b)(ii)

upright

Convex mirror has a wider viewthan a plane mirror.

Draw two incident rays andeach of them reflected at the

Shows image formed behindthe mirror and the position in

and diminished.(any of two combination)

Question 3: Kedah 07

Upright / diminished / smaller /

A radial ray that is incidentthrough the centre of

of the curved

is reflected back along theincident path through point CDetermine the correct position

To increase the field of vision

Question 6: SBP final F4 07Image that cannot be formed on

Image in Diagram 6.1 is bigger//

FIZIKMOZAC 2010

(c)

(d) Reflection(e) Wide angle of reflection // wider

the vision

6. Question 7: Trengganu 07(a) Two reflected rays are shown

(diagram)Angle of incidence = Angle of

reflection (diagram)

(a)(ii) Reflection(a)(iii) The driver in car P cannot see

car Q // field of view verysmall

(b)(i) Convex mirrorb(ii) Two reflected rays are shown

(diagram)Angle of incidence = Angle of

reflection (diagram)

(b)(iii) The convex mirror increasethe field of view

c(i) Unchangedc(ii) The characteristics of image

of a convex mirror notdepends on the focal length

5.2 REFRACTION OF LIGHT

7. Question 2: Melaka Mid 2010(a) Refraction(b) speed and direction of light

change when travel throughdifferent medium

(c) 49.5⁰(d) n = sin 49.5⁰ = 1.5

Sin 30⁰

8. Question 3: Melaka 07(a)(i)

Virtual / Magnified

(a)(ii)

Refraction

(b) Light ray travels from densityto less dense mediumRefracted away from normal.

(c) Draw refracted ray correctlyDraw ray from image to theobserver.

FIZIKMOZAC 2010

9. Question 5: Trengganu 08(a)(i)

Pencil in Diagram 6.2 morebending

(a)(ii)

Density of seawater is higher

(a)(iii)

The higher the density thegreater the bending

(b) The size of the pencil in thewater is greater

(c) Refraction(d) velocity(e)

10. Question 5: SBP 08(a) The gradient of the graph for

liquid X is higher than thegradient of the graph for water.

(b) The refractive index of water islower than the refractive indexof the liquid X.

(c) The higher the density of liquid,the higher the refractive index

(d) n = real depthapparent depth

= 1.00.6

= 1.67(e) Refraction of light(f) Wavelength increase.(g) The size of image seen from the

glass block is bigger.

11. Question 5: Kedah 09(a)(i) Speed of light in air is higherthan speed of light in water.(a)(ii) speed of light in air is higherthan speed of light in glass(a)(iii) If the speed of light decreases,then the light ray will bend towardsthe normal.(a)(iv) refraction(b)(i) One light ray from point P bendaway from the normal after emerginginto the airExtrapolate the ray to point Q.

(b)(ii) 1.6 = 1.331.2

5.3 TOTAL INTERNAL REFLECTION

12. Question 4: MARA 09(a)(i) critical angle(a)(ii) n = 1 = 1.5

Sin 42⁰(b)(i)

(b)(ii) i > 42⁰, so total internalreflection occurs

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(c)(ii) Angle of refraction will becomesmaller.

13. Question 4: Trengganu 07(a) Refractive index is the ratio of

sin i to sin r(b)(i)

( The refracted ray is closer to thenormal compare to the water )

(b)(ii)

The glass block is denser thanwater, so the light ray isrefracted more.

(c)(i)

The total internal reflection –angle of reflection is equal tothe angle of incidence.

(c)(ii)

The incident angle in thediamond is more than thecritical angle.

(d)Sin c = 1

n= 1

2.4c = 24.62 °

14.(i)

(ii) virtual, upright and same size(iii) final image of the binocular is

upright and it is shorter, solighter and easy to carry.

15. Question 2: Johor 08(a) Mirage(b)

Total internal reflection

(c)(i)

Density of the cool air is greaterthan the density of the warm air

(c)(ii)

The light rays will be refractedaway from the normal

(c)(iii

16.(a) Total internal reflection(b)(i) Q is denser(b)(ii) Q has higher refractive index.(c) sin c = 1 /2.1

c =(d)(i) endoscope

(ii) internet

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5.4 LENSES

17.(i)

(ii) real, inverted, magnified

(b)(i)

(b)(ii) virtual, upright, small

18.(a) image at the focal point(b) real, inverted, small(c) f = 19 – 9 = 10 cm(d) u = 15 cm(e

himage = v = 30 = 2hobject u 15

himage = 2 x 4 = 8 cm(f) real, inverted, magnified(g) at focal point

19. Question 2: SBP 08(a) Distance from the optical center

to the focus point.(b) 1 = 1 + 1

f u v

1 = 1 - 1v 2 3

= 16

v = 6 cm.(c)(i)

(ii) Real,inverted,magnified.

20.(a)(i)

(a)(ii) Real, inverted, magnified(b) 1 + 1 = 1

20 v 15v = 60 cm

(c) m = 60 = 320

(d) virtual, upright, smaller

21. Question 6: Mid Melaka 09(a) Image cannot be captured on the

screen(b)(i) Image in Diagram 6.1 is > then

Diagram 6.2(b)(ii) Equal // same

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(b)(iii) Image distance in Diagram 6.1is further// > than in Diagram5.2

(c) The shorter the image distancethe smaller the image //directlyproportional

(d) m = vu

(e)(i) blur(e)(ii) not enough light.

22. Question 8: Kelantan 08(a)

b Real, inverted, diminishedc(i)

1/f = 1/u + 1/vv = 15 cm

cii

m = v/um = 0.5

d(i)

Objective lens = convex lens YEyepiece lens = convex lens X

dii

Focal length convex lens Y >than focal length convex lens X

(d)(iii)

23. Conceptual: Kelantan 08 Density diagram 9.2 < density

diagram 9.3 Refractive index 9.2 < refractive

index 9.3 Angle of refraction in diagram 9.2 >

angle of refraction in diagram 9.3 The higher the density the smaller

the angle of refraction The higher the refractive index the

smaller the angle of refraction

24. Conceptual: Perak 07(i) Refraction / Total Internal

Reflection(ii) Block 1 (Rectangle)

:Refracted ray smaller thenthe incidence rayBlock 2(Prism) :The incidenceray is perpendicular and thereis no refracted raysAngles of incidence in theprism = Angles of reflection inthe prismRefractive index = 1

Sin cc= Critical angleThe ray of light comes from adense to a less densemedium orThe angle of incidence in thedense medium is greater thanthe critical angle

25. Conceptual: Johor 08(i) Ratio sin of incidence angle and

sine of refraction angle(ii) Refractive index digram9.2

larger than diagram 9.1Refraction angle diagram 9.2 issmaller than diagram 9.1Critical angle diagram 9.1larger than diagram 9.2When the refractive index islarge, the critical angle is small

FIZIKMOZAC 2010

26. Conceptual: Melaka 08(i) A point at principle focus where

light ray parallel with principleaxis converge/diverge to/from it.

(ii) 1.Convex lens K more thicknessthan lens J

2.The light rays refracted andconverge to the point F

3.The distance between O and Fis focal length.

4.Focal length lens K is shorterthan lens J

5.More thickness the lens ,shorter the focal length

27. Conceptual: Melaka 08(a)(i) Real image is an image which

can be seen on a screen.(a)(ii) the object distance in

diagram 10.1 is longerthan diagram 10.2

the image distance indiagram 10.2 is longerthan diagram 10.1

the size of the image indiagram 10.2 is larger

the longer the imagedistance, the bigger thesize of the image

The smaller the objectdistance the larger thesize of the image / theobject distance isinversely proportional tosize of the image.

28. Conceptual: SBP 08 The object distance in Diagram 9.1

is closer than in Diagram 9.2 The image distance in Diagram 9.1

is further than in Diagram 9.2 The size of image in Diagram

9.1 is larger than in Diagram9.2

The further the object distance,the closer the image distance

The further the object distance,the smaller the size of image

29. Understanding: SBP 08i. Concave mirror(i) Show object at the correct

distance , u < fRay parallel to the principal axisreflect through the focal pointIntersection of 2 reflected raysbehind the mirror.

30. Understanding: Melaka 08 The convex lens with its holder is

aimed at a distant object like atree.

Adjust a screen until you see avery sharp and clear image of thedistant object.

When parallel light rays from adistant object pass through aconvex lens, they will converge toa point called focal point/ label ona diagram

Measure the distance between theconvex lens and screen./ label ona diagram

FIZIKMOZAC 2010

31. Understanding: Kelantan 08(i) Angle between incident ray and

normal line(ii) Increase the angle of

incidence, i, then angle ofrefraction, r, will also increase

Keep on increasing the angleof incidence until angle ofrefraction is 90˚

The angle of incidence iscalled critical angle

Increase the angle ofincidence more than thecritical angle

The ray will be totallyreflected.

32. Understanding : Johor 081. the angle of incidence is greater

than critical angle2. the light travel from medium high

density to low density

33. Understanding: SBP 08 The layers of air nearer the road

warmer. The density of air decrease

nearer to the road surface. The light travel from denser to

less dense area. The light refract away from the

normal

Understanding: Kelantan 08Angle between incident ray and

Increase the angle ofincidence, i, then angle ofrefraction, r, will also increaseKeep on increasing the angleof incidence until angle of

The angle of incidence is

Increase the angle ofincidence more than the

ll be totally

Understanding : Johor 081. the angle of incidence is greater

2. the light travel from medium high

Understanding: SBP 08The layers of air nearer the road

density of air decreasenearer to the road surface.The light travel from denser to

The light refract away from the

When the angle of incidenceexceed the critical angle, totalinternal reflection occurs

34. Understanding: Perak1. Draw a diagram to show the rays

of light2. Total internal reflection3. 180 0 fish eye view4. Obstacle

35. Understanding: Kedah 071. Diagram shows a curved optical

fibre (with outer and internallayer) with at least two totalinternal reflection

2. The refractive index of theinternal layer of the optical fibreis greater than the external layeror air

3. Angle of incidence,angle, c

4. Total internal reflection occur

36. Understanding: MRSM 07(i) Convex mirror(ii) Has a wider view

Upright image The image is seen at a

distance v ≤ f behind themirror for all positions of theobject

(iii) Light ray from object that isparallel to the principal axisis reflected as if it comesfrom the focal point

Position of the image

When the angle of incidenceexceed the critical angle, totalinternal reflection occurs

Understanding: Perak 07Draw a diagram to show the rays

Total internal reflection

Understanding: Kedah 07Diagram shows a curved opticalfibre (with outer and internallayer) with at least two total

The refractive index of theinternal layer of the optical fibreis greater than the external layer

Angle of incidence, i > critical

Total internal reflection occur

Understanding: MRSM 07

Has a wider view

The image is seen at a≤ f behind the

mirror for all positions of the

Light ray from object that isparallel to the principal axisis reflected as if it comesfrom the focal pointPosition of the image

FIZIKMOZAC 2010

37. Understanding: Johor 07

(a)Periscope SAll the light is reflected into theeyes of the viewer through total

internal reflection.

(b)R

Position of mirror//position ofprisms

Ray diagram for R and S Condition: Light ray travels

from optically dense mediumto optically less densemedium, or angle of incidencemore than critical angle

38. Qualitative problem: Perak 07

(i) Draw a correct ray diagram withat least 2 raysBoxUsing two right-angled prismsArrangement of prismTotal internal reflection

(ii) Draw a diagram to showarrangementRight angle prism which causethe the rays to bent through 1800

4 prism2 eye piece2 objective lens

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39. Qualitative problem: Johor 08Aspect Reason

1. An inner coreof higherrefractive index

Light ray isreflected moreeasily throughtotal internalreflection

2. Outer layer ofmedium with alower refractiveindex

Light ray isreflected moreeasily throughtotal internalreflection

3. Lower density The optical fibrewill be lighter

4. The thicknessof the glass isthin

Save pace / canbe used innarrowspace

5. Strong andflexible

Does not breakeasily and theshape can beadjusted

40. Qualitative: SBP 08(i) Objective lens above // diagram

Eyepiece below // diagramCorrect arrangement of prisms //diagram

(ii) Ray from object to the 1and reflect 90Second reflection 90Reflection in 2nd prism (double

problem: Johor 08Reason

Light ray isreflected moreeasily throughtotal internalreflectionLight ray isreflected moreeasily through

internalreflectionThe optical fibrewill be lighterSave pace / canbe used in

Does not breakeasily and theshape can beadjusted

Objective lens above // diagramEyepiece below // diagramCorrect arrangement of prisms //

Ray from object to the 1st prism

in 1st prismprism (double

reflection)Draw another ray diagram

(iii) Shorter // smaller size of binocular// easy to carryProduce upright image

41. Qualitative: Melaka 08(i) draws the objective and

eyepiece lenses. correct label of objective and

eyepiece label fO and fe

draw the correct position forthe object ( fo

draw ray diagrams to show theposition of image 1

draw ray diagrams to show thefinal image

(ii) Use a concave mirror Converge light to the

microscope.(iii) Decrease the object distance /

decrease the focal length ofthe eyepiece lens / decreasethe focal length of theobjective lens.

increase the magnificationfactor.

another ray diagram

Shorter // smaller size of binocular

Produce upright image

Qualitative: Melaka 08draws the objective andeyepiece lenses.correct label of objective and

correctlycorrect position for

< u1 < 2fo)draw ray diagrams to show theposition of image 1draw ray diagrams to show the

Use a concave mirrorlight to the

Decrease the object distance /the focal length of

the eyepiece lens / decreasethe focal length of theobjective lens.increase the magnification

FIZIKMOZAC 2010

42. Making decision: Johor 07

(a) Design Z Concave mirror converges all

the light to the focal point(b) Use spherical disc of

concave mirror so that morelight is converge to the focalpoint, hence the intensity oflight is high

The kettle holder is made ofiron

Which is a good conductor ofheat.

(c) No pollution Renewable

(d) Restriction of the weather High cost Need a large area Difficult to stop and transfer

to ac form

43. Making Decision: Kedah 07

(i) refractive index =Speed of light in vacuumSpeed of light in the medium

Characteristics ReasonHigh refractiveindex

Total internalreflection canoccur easily

Small amount oflight energybeing absorbedby the material

The object underobservation canbe seen clearly //more light can betransmitted

Material withweak rigidity

The optical fibrecan be bent easily

Material withstrong strength

The optical fibrecan last longer/noteasily spoil

Material R High refractiveindex, low % oflight energyabsorbed, weakrigidity and strongstrength

44. Making Decision: MRSM 07(i) Diameter of fibre should be

small The endoscope is small /

slim Material should be strong

and of high flexibility Bends easily without

breaking The refractive index of the

inner layer is greater thanthe refractive index of theouter layer.

Total internal reflection canoccur

The most suitable is R Because the diameter is

small, high flexibility andrefractive index of the innerlayer is greater than theouter layer.

(ii) Objective lens: to form theimage of an object

Eye piece: to focus theimage

45. Quantitative problem: MRSM 07(i) u = 30 cm, f = -10 cm

1/v = 1/-10 – 1/30v = - 7.5 cm

(ii) m = v/u= 7.5/30= 0.25

FIZIKMOZAC 2010

46. Quantitative problem: Kedah 07(i) The coin appear bigger when

seen by observer BThe coin is nearer to theobserver B

(ii)

= 12 cm

(iii) Add in more water//add in somesalt solution

47. Section B:Kelantan 09(a) Distance between optical centre

and focal point.(b) Lens in Diagram 9.1 is thinner Focal length in Diagram 9.1 is

longer. Power of lens in Diagram 9.1 is

lower. The thinner the lens the longer

the focal length The thinner the lens, the lower

the power of the lens.(c)(i) at u < f

(d)Modification explanation

P as eye piecelens and Q asobjective lens

Focal length of Pis longer

Fo < u < 2fo To produce real,inverted andmagnified image

Adjusted so thatu < fe

To producevirtual, invertedand bigger image

// to acts as amagnifying glass

Distance betweenlenses > fo + fe

To producebigger imagefrom the eyepiece// to increase themagnification

Store in a cooland dry place

To avoid fungusin the lenses.

48. Section B: Melaka 09(a)(i) Incident angle when its

refracted angle is 90o

(a)(ii) Incident angle in Diagram 9.1 <

Incident angle in Diagram 9.2 Diagram 9.1 refraction Diagram 9.2 total internal

reflection Incident angle in Diagram 9.1 is

less than critical // incident anglein Diagram 9.2 is more thancritical angle

when incident angle more than thecritical angle total internalreflection occurred

(b) Light consisting of seven colours Red has the longest wave length

and the last to refracted duringsunset

A droplet of water trap in theatmosphere after raining acts alens

Light travel through this waterdroplet and undergo the processof refraction ,total internalreflection and dispersion of lightoccurred

x

16

3

4=

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(c)(i) Optical fibber consist two layers

from two types of glass. it consists of core at the centre

and outer layer with differencerefractive index

The outer layer glass has lowerrefractive index than the innercore glass.

When the angle of incidence oflight is greater than the criticalangle

light rays undergo total internalreflection

repeatedly until they emerge fromthe opposite end of the opticalfibre.

(c)(ii)Modification Reason

Built bundle ofoptical fiber

Carry moreinformation

strong material not easily breakVery flexible Easy to bend at

the curve part