Question 1

The Balmer Series of lines in the hydrogen atom was very important in the history of physics and astronomy. What made it so important?

Accepted Answer

A)  It helped Rutherford explain the workings of the atomic nucleus 
B)  Balmer's experiments with these lines helped prove Wien's Law 
C)  When electrons change levels to produce the Balmer series, the emitted light is in the visible part of the spectrum, so the lines were easy to see with our eyes 
D)  The Balmer series of lines can only be observed from outer space; so the competition to see these lines led to the space race 
E)  Mr. Balmer never got the Nobel prize, which made everyone in the field of spectroscopy so angry, they worked extra hard

Question 2

We observe a glowing cloud of gas in space with a spectroscope. We note that many of the familiar lines of hydrogen that we know on Earth seem to be in a different place. They are shifted toward the blue or violet end of the spectrum compared to their positions in the spectrum of glowing hydrogen gas on Earth. From this we can conclude that:

Accepted Answer

A)  the cloud is much hotter than hydrogen on Earth 
B)  the cloud is much cooler than hydrogen on Earth 
C)  the cloud is moving toward us 
D)  the cloud is moving away from us 
E)  none of the above can be concluded from this observation.

Question 3

The light which allows you to see this very interesting exam is made up of waves. In these waves, the distance between crests is called the:

Accepted Answer

A)  frequency 
B)  velocity 
C)  wavelength 
D)  amplitude 
E)  you can't fool me; in these waves, the distance between crests is zero

Question 4

Two stars have the same diameter and are at the same distance from us (but in different parts of the sky.) Star A has a temperature of 4000 K, while star B has a temperature of 8000K. Which of the following statements is true:

Accepted Answer

A)  the two stars have the same total energy flux (luminosity) 
B)  star B has twice the energy flux (luminosity) that star A has 
C)  star B has one half the energy flux (luminosity) that star A has 
D)  star B has 16 times the energy flux (luminosity) that star A has 
E)  Sorry, professor, we don't have enough information to compare the energy flux (luminosity) of the two stars
Section 5.3: Spectroscopy in Astronomy

Question 5

Which of the following is not a type of electromagnetic wave with lower energy than visible light waves?

Accepted Answer

A)  microwaves 
B)  radar waves 
C)  the waves that carry AM or FM broadcasts 
D)  the sound waves coming from your transistor radio 
E)  the waves that carry television transmissions

Question 6

The fastest speed in the universe is:

Accepted Answer

A)  the speed of sound 
B)  the speed of light 
C)  the speed of electron oscillations 
D)  the speed with which Mercury orbits the Sun 
E)  the speed with which weekends seem to pass

Question 7

The energy of random atomic and molecular motion is called

Accepted Answer

A)  heat 
B)  the Doppler shift 
C)  spectroscopy 
D)  reflection 
E)  rock and roll

Question 8

You are alone in a large, completely dark auditorium on Earth. What kind of telescope should I use from the other side of the auditorium to detect the electromagnetic radiation emitted by your body?

Accepted Answer

A)  visible light 
B)  infra-red 
C)  ultra-violet 
D)  black light 
E)  no telescope will be effective if I am in a dark room

Question 9

An idealized object that does not reflect or scatter any radiation that hits it, but simply absorbs every bit of radiation that falls on it is called:

Accepted Answer

A)  a Doppler surface 
B)  an electromagnetic radiator 
C)  a blackbody 
D)  a spectrum 
E)  a vice president

Question 10

The idea that atoms radiate energy only when their electrons move from higher to lower energy levels was first advanced by:

Accepted Answer

A)  J. J. Thomson 
B)  Niels Bohr 
C)  Ernest Rutherford 
D)  Albert Einstein 
E)  Christian Doppler

Question 11

(In the absence of a strong magnetic field), what is the chief factor that determines what type of electromagnetic radiation objects give off:

Accepted Answer

A)  their mass 
B)  their temperature 
C)  their distance from the Earth's center 
D)  their chemical makeup 
E)  their size

Question 12

Of the following, which consists of electro-magnetic waves with the shortest wavelength?

Accepted Answer

A)  a beam of green light 
B)  TV transmissions bringing us Monday night football 
C)  the sound of the instructor's voice 
D)  the waves of a dental x-ray 
E)  the rays that tan a sunbather on the beach

Question 13

What happens as an electron falls from a higher level to a lower level in an atom?

Accepted Answer

A)  a photon is given off 
B)  the color of the wave involved shifts to the red 
C)  a photon is absorbed 
D)  another electron from the lower level takes its place 
E)  nothing happens; electrons can only go from a lower level to a higher level

Question 14

Which of the following statements about electromagnetic radiation is FALSE?

Accepted Answer

A)  it always spreads out at the speed of light 
B)  it is given off by all objects that are not at a temperature of absolute zero 
C)  it is typically produced when charged particles oscillate 
D)  different waves of electromagnetic radiation differ in their wavelength or frequency 
E)  the radiation consists of tiny charged particles given off by the nuclei of atoms

Question 15

One reason that human eyes evolved to detect visible light is:

Accepted Answer

A)  it is the band of the electromagnetic spectrum with the lowest possible energy and thus easiest to detect 
B)  it is the only band of the spectrum that can travel through a vacuum 
C)  it is the band of the spectrum which is the least Doppler shifted coming from the Sun 
D)  it is a band of the spectrum where the Sun puts out a great deal of energy 
E)  it is the band of the spectrum where the warm Earth glows the most effectively at night

Question 16

Most ultraviolet radiation does not penetrate to the Earth's surface. Instead it is absorbed in:

Accepted Answer

A)  the ozone layer 
B)  the ionosphere 
C)  the region between the Earth and the Sun 
D)  stratosphere 
E)  tanning zone

Question 17

How fast do electro-magnetic waves travel?

Accepted Answer

A)  at the speed of sound 
B)  at the speed of light 
C)  at the speed of charge 
D)  at different speeds, depending on the temperature of the atoms that produce them 
E)  they always have zero speed

Question 18

An astronomer discovers a new star and wants to measure its temperature. She would typically do this by:

Accepted Answer

A)  measuring the Doppler shift of its spectral lines 
B)  making a blackbody curve and finding the wavelength of the peak (maximum) 
C)  measuring the intensity of radio waves the star gives off 
D)  measuring how much light the star reflects 
E)  sending a graduate student with a very long (and durable) thermometer to the star's vicinity

Question 19

When a star or galaxy is moving away from us, we observe the Doppler effect by seeing the lines in its spectrum

Accepted Answer

A)  red-shifted (shifted toward the red end of the light spectrum) 
B)  blue-shifted (shifted toward the blue or violet end of the light spectrum) 
C)  yellow-shifted (shifted so all the colors become a little bit yellower) 
D)  become darker and darker (like a blackbody) 
E)  you can't fool me, the Doppler effect only applies to motions on Earth, not to the motions of the stars and galaxies

Exam 5: Radiation and Spectra