QUIZ 1 - AY4 - W04 . . . . . . . . . . . . . . YOUR NAME:
Mike
Possibly useful formulae:
λmax (cm) =
0.29
T(K) ;
λ × f = c (wavelength x frequency = speed)
Speed of light = c = 300,000 km/sec
1. How long does it take light to travel from the Moon to the Earth, a distance of 384,000 km? By
the way, did you remember to write your name on the quiz?
Time=Distance/Speed=3.84x10 5 km
3x10 5 km
sec
3.84
=
seconds
3
2. The reason we experience different seasons is:
a) The Earth’s orbit around the Sun is an ellipse so sometimes we are closer to the Sun (summer), sometimes
we are further from the Sun (winter).
b) The Earth spins on its axis.
c) The spin axis of the Earth around its center is tilted with respect to the orbital axis of the Earth around
the Sun.
c) None of these answers is correct.
3. The speed of light is c = 186, 000 miles/second. Calculate the speed of light in units of
miles/minute.
186,000
miles
second
x
60 seconds
= 186,000 x 60 miles/minute
minute
4. Rank the following in order of increasing frequency (1 - highest; 5 - lowest):
1 X-rays
4 FM radio (800 MegaHertz)
2 Blue light
5 AM radio (800 kiloHertz)
3 Infrared
5. A source emits infrared radiation at a wavelength of 1060×10−9 m. What is the frequency of this
radiation?
f=c/ wavelength =
3x10
5
km/sec
1km
−9
m
x
1060 x 10
1000m
=
3
1060
17
x 10 1/sec
6. Suppose you have a hot (i.e. collisionally excited) gas of hydrogen and a hot gas of helium, each
at the same temperature. Label the following statements True (T) or False (F).
f The two gases would have identical spectra
f Both gases would show identical emission-line spectra
t The two gases would show different emission-line spectra
f Both would show continuous spectra, with the helium-gas spectrum peaking at a shorter wavelength