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
