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Thursday, March 29, 2012

Doppler Shift

8
a Which transition

Use of (
Δ)E = hc/λ OR (Δ)E = hf and f = c/λ 1

Use of 1.6 x 10
-19 1

Correct answer [1.9 eV]
1

C to B / -1.5 to – 3.4
1 4

[Accept reverse calculations to find wavelengths]

e.g.

(6.63 x 10
-34 J s)(3.00 x 108 m s-1)/

(656 x 10
-9 m)(1.6 x 10-19 J eV-1)

= 1.9 eV

b Explanation of absorption line

QOWC
1

Light of this wavelength is absorbed by hydrogen
1

In the outer part of the Sun (OR Sun’s atmosphere)
1

Absorbed radiation is reemitted in all directions
1

Transition from B to C (OR -3.4 to -1.5)
1 Max 4

c i Why galaxy receding

Wavelength increased (OR stretched) / red shift /

frequency decreased

1

c ii Calculation of speed

Use of
v/c = Δλ/λ 1

Correct answer [1.78 x 10
7 m s-1] 1 3

e.g.

(3.00 x 10
8 m s-1)(695 x 10-9 m – 656 x 10-9 m)/

(656 x 10
-9 m)

= 1.78 x 10
7 m s-1

[N.B. Use of wrong wavelength in denominator gives

1.68 x 10
7]

OR

Use of
v = fλ and v/c = Δf/f 1

Correct answer [1.67 x 10
7 m s-1] 1

[Look for

(4.573 x 10
14 Hz – 4.317 x 1014 Hz) / (4.537 x 1014 Hz)

N.B. Use of wrong frequency in denominator gives 1.78

x 10
7]

Total 11