1. Why is the sky blue?
(A) Because the oxygen in air is absorbing reddish light, so the remaining light has a bluish tinge.
(B) Because blue light is refracted more strongly than red light.
(C) Because the probability for light scattering increases with the light frequency to the 4th power.
(D) Because blue light is diffracted more strongly than red light.
(E) Because the water vapor in the air absorbs red light (vibrational overtones), so the remaining light has a bluish tinge.

2. Why is the sky blue?
(A) Because the oxygen in air is absorbing reddish light, so the remaining light has a bluish tinge. Baloney
(B) Because blue light is refracted more strongly than red light.
while blue light is indeed refracted more strongly, that doesn’t
make the sky blue.
(C) Because the probability for light scattering increases with the light frequency to the 4th power. CORRECT! This results in blue
light scattered more strongly. When we look at the sky, we see the scattered light.
(D) Because blue light is diffracted more strongly than red light Wrong ... it’s the other way around.
(E) Because the water vapor in the air absorbs red light (vibrational overtones), so the remaining light has a bluish tinge.
That is what gives water a bluish color, but not the sky.

3. { Which of the processes indicated below will be observed? I II III
Energy
Virtual Energy
Level
1st excited
vibrational state
ground state
DE = Evib {
hn0
hn0-Evib
hn0+Evib
I II III
Only process I.
Processes I and II.
All three processes.

4. { Which of the processes indicated below will be observed? I II III
Energy
Virtual Energy
Level
1st excited
vibrational state
ground state
DE = Evib {
hn0
hn0-Evib
hn0+Evib
I II III
Only process I.
Processes I and II.
All three processes.

5. Recall the selection rules for purely rotational microwave spectra: DJ = ±1. This came from angular momentum conservation (a photon
has spin angular momentum ħ). In Raman scattering, one photon
comes in and one photon goes out. What do you think are the selection
rules for rotational Raman transitions?
(A) DJ = ±1
(B) DJ = 0, ±1, ±2
(C) DJ = 0, ±2
(D) DJ = 0

6. Recall the selection rules for purely rotational microwave spectra: DJ = ±1. This came from angular momentum conservation (a photon
has spin angular momentum ħ). In Raman scattering, one photon
comes in and one photon goes out. What do you think are the selection
rules for rotational Raman transitions?
(A) DJ = ±1
(B) DJ = 0, ±1, ±2
(C) DJ = 0, ±2 *
(D) DJ = 0
* makes sense, because a photon comes in and transfers one unit of ħ to the molecule, and one photon comes out again, which again has one unit of ħ. If the incoming and outgoing photons have the same spin, DJ = 0. If they have opposite spins, DJ = ±2.