• Physics trip: Monday 8th April

• Need payment and permission slips back by Friday

• Reminder: internal – last week of term

• Tasks to complete:

homework and old exam questions (nuclear and photo-electric effect)

• We have one more topic to cover before the internal: atomic spectra

homework set and old exam questions for this also

Student feedback:

H/W books

Textbook work

Do now / starter activities

Revision booklets

Worksheets

Playing with the diffraction grating and lasers

Doppler applications (speed radar, expansion of the universe)

Estimating and processing uncertainties

Experiment 1: measuring standing waves with ticker timers

Experiment 2: measuring the wavelength of a laser using a diffraction grating

Video clips

Phet animations

Ruben tube demo

Mini tests

Do the sticker timeline

Notes on Bohr’s model

photons of white light(all frequencies)

shone through a sample of gas

most frequencies pass straight through

but some are absorbed

and re-emitted (in random directions)

Absorption spectrum: dark lines indicate the “missing” frequencies (the absorbed photons)

Where would you place the spectrometer to detect the emitted photons? (the emission spectrum)

The Hydrogen SpectrumThe Hydrogen Spectrum

1 2 3 4 5

Lyman Series S=1 (UV)

Balmer Series S=2 (visible)

Paschen Series S=3 (IR)Bracket Series S=4 (IR)

Pfund Series S=5 (IR)

Nucleus

Shell no. / Energy level

The Hydrogen SpectrumThe Hydrogen Spectrum

The wavelengths of the emitted photons are The wavelengths of the emitted photons are given by:given by:

R=Rydberg’s Constant=1.097x10R=Rydberg’s Constant=1.097x1077 m m-1-1

S=Series no. (the shell jumped into)S=Series no. (the shell jumped into)L=Line no. (the shell jumped from)L=Line no. (the shell jumped from)

22

111

LSR

Bohr’s Model of the AtomBohr’s Model of the Atom

The energy levels in the Hydrogen atom are The energy levels in the Hydrogen atom are given by :given by :

h=Plancks constant = 6.63x10h=Plancks constant = 6.63x10-34-34 Js Js c=speed of light = 3x10c=speed of light = 3x108 8 msms-1-1

R=Rydbergs constant = 1.097x10R=Rydbergs constant = 1.097x1077 m m-1-1

n=energy level = 1,2,3,4…… (quantum number)n=energy level = 1,2,3,4…… (quantum number)

2n

hcREn

Bohr’s Model of the AtomBohr’s Model of the Atom

-1

-2

Energy

(x10-18J)

0

n=1

n=2

n=3n=4

n=∞

181

2

7834

1

1018.2

1

10097.11031063.6

E

E

QuestionsQuestions

1)1)Calculate the wavelength and frequency of the Calculate the wavelength and frequency of the first line in the Balmer seriesfirst line in the Balmer series

2)2)An electron in a hydrogen atom falls from the An electron in a hydrogen atom falls from the third to the second energy levelthird to the second energy level

a) How much energy does the electron lose?a) How much energy does the electron lose?

b) What is the energy of the photon emitted?b) What is the energy of the photon emitted?

c) What is the frequency of the emitted photon?c) What is the frequency of the emitted photon?

textbook p182

textbook p187