Question

Question 2 (1 point) The Weak Interaction is weak because Question 2 options:

To interact weakly requires the creation of a heavy gauge boson

Not many particles participate in it

Particles that interact weakly do so at a great distance

The weak interaction involves neutrinos which are rare

Question 3 (1 point) All other things being equal, which of the following conditions would result in more nuclear reactions taking place each second inside the Sun than is currently the case ?

Question 3 options: If the electric charge of the reacting nuclear particles were smaller than they are If the core temperature was lower than it is.

If the core density was lower than it is

Both A and B would result in more nuclear reactions per second

Both A and C would result in more nuclear reactions per second

Question 16 (1 point)

Dark lines appear at certain frequencies in stellar spectra because

Question 16 options:

	Less light is emitted from the photosphere at those frequencies than is emitted at neighboring frequencies.
	light at those frequencies gets absorbed by gases in the stellar atmosphere
	Neither of the above
	Both explanations contribute almost equally to the effect

Question 17 (1 point)

Absorption lines of Hydrogen are almost absent from type O stars because

Question 17 options:

	O stars are so cold that only a tiny proportion of photons have enough energy to cause atomic transitions in Hydrogen
	O stars have only a tiny proportion of Hydrogen in their atmospheres
	There is so little flux radiated at the proper frequencies that you cannot notice the reduction in flux due to absorption.
	There is so much flux at ionizing frequencies that very little absorption takes place

Question 5 (1 point)

Saved

The quantity that uniquely and quantitatively determines the opacity of a gas is

Question 5 options:

	Gas density
	Mean Free Path
	Random Walk
	Temperature

Question 6 (1 point)

Saved

A ten solar mass star has about ten times the sun's supply of nuclear energy. Its luminosity is 1000 times that of the sun. How does the lifetime of the star compare with that of the sun?

Question 6 options:

	10 times longer
	the same
	10 times shorter
	100 times shorter

Answer 1

16-b

The dark lines in stellar spectra are caused by the absorption of specific wavelengths of energy by elements in the star's outer levels. Identifiable patterns of absorption lines that appear at shorter or longer wavelengths than normal indicate that the star is moving.

17-a

If the star is too hot or too cold, the hydrogen lines will be weak. To produce strong, dark hydrogen lines, the star's temperature must be within a certain range. ... Calcium atoms have a looser hold on their electrons so calcium lines are strong for cooler temperatures of 3000 to 6000 K.

5-b5-b mean free path