Deck 4: Light

Question 1

A hotter star will radiate more blue photons than a cooler star.

Answer 1

False

Question 2

A thin cloud of cool gas on top of hotter blackbody will radiate an emission spectrum.

Answer 2

False

Question 3

The total number of neutrons and protons define an atom's atomic mass and determine the type of chemical element it is.

Answer 3

False

Question 4

The energy of a proton is inversely proportional to its wavelength.

Question 5

The speed of light was first determined by which scientist?

A) Galileo
B) Rømer
C) Kepler
D) Newton
E) Einstein

Question 6

The emission spectrum of a helium atom is identical to that of a carbon atom.

Question 7

It is possible for light to travel slower than 300,000 km/s.

Question 8

According to quantum mechanics,it is possible to determine beforehand when a given atom will spontaneously decay.

Question 9

If an object is moving toward you,the light you see from it will be blueshifted.

Question 10

The emission and absorption lines of a given atom occur at the exact same energies.

Question 11

Cooler objects radiate more of their total light at shorter wavelengths than hotter objects.

Question 12

A radio photon travels more slowly than a gamma ray photon.

Question 13

The reason that Earth is hotter than Jupiter is because the Earth is smaller than Jupiter.

Question 14

Doppler shift can be used to determine the 3-dimensional velocity of a star.

Question 15

Heisenberg's uncertainty principle tells us that an electron in an atom behaves more like a cloud than a pointlike particle.

Question 16

The period of a wave is inversely proportional to the frequency of the wave.

Question 17

The luminosity of an object is independent of its distance from you.

Question 18

In our solar system,a planet's temperature depends primarily on its albedo and distance from the Sun.

Question 19

An emission line is produced when an atom absorbs a photon of a specific energy.

Question 20

The speed of light in a vacuum is __________.

A) 300,000 m/s
B) 300,000 mph
C) 300,000 km/s
D) 300,000,000 mph
E) infinite

Question 21

Why is an iron atom a different element than a sodium atom?

A) A sodium atom has fewer neutrons in its nucleus than an iron atom.
B) An iron atom has more protons in its nucleus than a sodium atom.
C) A sodium atom is bigger than an iron atom.
D) All of the above are true.

Question 22

A star emits

A) an absorption spectrum.
B) a continuous spectrum.
C) an emission spectrum.
D) no radiation.

Question 23

The fact that the speed of light is constant (as it travels through a vacuum)means that

A) photons with longer wavelengths have lower frequencies.
B) radio wave photons have shorter wavelengths than gamma ray photons.
C) X-rays can be transmitted through the atmosphere around the world.
D) All of the above are true.

Question 24

Which formula denotes how the speed of light is related to its wavelength and frequency?

A)
B)
C)
D)

Question 25

As wavelength increases,the energy of a photon __________ and its frequency __________.

A) increases;decreases
B) increases;increases
C) decreases;decreases
D) decreases;increases

Question 26

You are driving on the freeway when a police officer records a shift of -7 nm when he hits you with a radar gun that operates at a wavelength of 0.1 m.How fast were you going?

A) 47 mph
B) 83 mph
C) 21 mph
D) 65 mph

Question 27

How do the wavelength and frequency of red light compare to the wavelength and frequency of blue light?

A) Red light has a longer wavelength and higher frequency than those of blue light.
B) Red light has a longer wavelength and lower frequency than those of blue light.
C) Red light has a shorter wavelength and higher frequency than those of blue light.
D) Red light has a shorter wavelength and lower frequency than those of blue light.

Question 28

In the quantum mechanical view of the atom,an electron is best thought of as

A) a cloud that is centered on the nucleus.
B) a pointlike particle orbiting the nucleus.
C) free to orbit at any distance from the nucleus.
D) All of the above are true.

Question 29

If the wavelength of a beam of light were to double,how would that affect its frequency?

A) The frequency would be four times larger.
B) The frequency would be two times larger.
C) The frequency would be two times smaller
D) The frequency would be four times smaller.
E) There is no relationship between wavelength and frequency.

Question 30

The Doppler shift can be used to determine the __________ of an object.

A) energy
B) temperature
C) radial velocity
D) no radiation

Question 31

When an electron moves from a higher energy level in an atom to a lower energy level,

A) the atom is ionized.
B) a continuous spectrum is emitted.
C) a photon is emitted.
D) a photon is absorbed.

Question 32

The light-year is a unit of

A) time.
B) distance.
C) speed.
D) energy.

Question 33

A red photon has a frequency of 650 nm.An ultraviolet photon has a frequency of 250 nm.The energy of an ultraviolet photon is __________ than a red photon.

A) 2.6 times larger
B) 6.8 times larger
C) 2.6 times smaller
D) 6.8 times smaller

Question 34

Einstein showed that the __________ could be explained if photons carried quantized amounts of energy.

A) warping of space and time
B) Heisenberg uncertainty principle
C) photoelectric effect
D) theory of special relativity

Question 35

Which of the following photons carry the least amount of energy?

A) a blue photon of the visible spectrum,whose wavelength is 450 nm
B) an infrared photon,whose wavelength is
C) a red photon in the visible spectrum,whose wavelength is 700 nm
D) a microwave photon,whose wavelength is

Question 36

A nebula emits

A) an absorption spectrum.
B) a continuous spectrum.
C) an emission spectrum.
D) a rainbow spectrum.

Question 37

The electronic energy level in a hydrogen atom is J higher than the level.If an electron moves from the level to the level then a photon of wavelength

A) 1.3 nm,which is in the ultraviolet region,is emitted.
B) 1.3 nm,which is in the ultraviolet region,is absorbed.
C) 1,300 nm,which is in the infrared region,is absorbed.
D) 1,300 nm,which is in the infrared region,is emitted

Question 38

Which of the following lists different types of electromagnetic radiation in order of increasing wavelength?

A) Radio waves,infrared,visible,ultraviolet,X-rays
B) Gamma rays,ultraviolet,visible,infrared,radio waves
C) Gamma rays,X-rays,infrared,visible,ultraviolet
D) X-rays,infrared,visible,ultraviolet,radio waves
E) Radio waves,ultraviolet,visible,infrared,gamma rays

Question 39

How does the speed of light traveling through a medium (such as air or glass)compare to the speed of light in a vacuum?

A) It is the same as the speed of light in a vacuum.
B) It is always less than the speed of light in a vacuum.
C) It is always greater than the speed of light in a vacuum.
D) Sometimes it is greater than the speed of light in a vacuum,and sometimes it is less,depending on the medium.

Question 40

Light with a wavelength of 600 nm has a frequency of

A) .
B) .
C) .
D) .

Question 41

Describe,in your own words,the fundamental problem with the Bohr model of the atom.(That is,why doesn't an electron orbit a nucleus like a planet does the Sun?)

Question 42

The average red giant in the night sky is about 1,000 times more luminous than the average main-sequence star.If both kinds of stars have about the same brightness,how much farther away are the red giants compared to the main-sequence stars?

A) 32 times farther
B) 1,000 times farther
C) 65 times farther
D) The red giants and main sequence stars have approximately the same distances.

Question 43

At what temperature does water freeze?

A) 0 K
B) 32 K
C) 100 K
D) 273 K
E) 373 K

Question 44

An asteroid with an albedo of 0.1 and a comet with an albedo of 0.6 are orbiting at roughly the same distance from the Sun.How do their temperatures compare?

A) They both have the same temperature.
B) The comet is hotter than the asteroid.
C) The asteroid is hotter than the comet.
D) You must know their distance to compare their temperatures.

Question 45

Star C and star D are equally luminous.Star C is twice as far away from Earth as star D.How do the brightness level of stars C and D compare?

A) Star C appears four times as bright as star D.
B) Star C appears twice as bright as star D.
C) Star D appears twice as bright as star C.
D) Star D appears four times as bright as star C.

Question 46

At what wavelength does your body radiate the most given that your temperature is approximately that of the Earth,which is 300 K?

A)
B)
C)
D)
E)

Question 47

Which of the following factors does NOT directly influence the temperature of a planet?

A) The luminosity of the Sun
B) The distance of the planet from the Sun
C) The albedo of the planet
D) The size of the planet

Question 48

Name four physical properties of an object that we can determine by analyzing the radiation that it emits,and briefly describe how these properties are determined.Cite the names of any laws that apply.

Question 49

As a blackbody becomes hotter,it also becomes __________ and __________.

A) more luminous;redder
B) more luminous;bluer
C) less luminous;redder
D) less luminous;bluer

Question 50

The difference in energy between the and electronic energy levels in the hydrogen atom is .If an electron moves from the level to the level will a photon be emitted or absorbed? What will its energy be,and what type of electromagnetic radiation is it?

Question 51

You record the spectrum of a star and find that the calcium absorption line,whose rest wavelength is 393.3 nm,has an observed wavelength of 394.0 nm.What is the radial velocity of this star?

A) 500 km/s
B) 50 km/s
C) 5 km/s
D) 0.5 km/s

Question 52

The Kelvin temperature scale is used in astronomy because

A) at 0 K an object has absolutely zero energy.
B) water freezes at 0 K.
C) water boils at 100 K.
D) hydrogen freezes at 0 K.

Question 53

Consider an incandescent light bulb.If you wanted to turn a 10 W light bulb into a 100 W light bulb,how would you change the temperature of the filament inside the bulb?

A) Raise its temperature by a factor of 3.2
B) Raise its temperature by a factor of 1.8
C) Lower its temperature by a factor of 2.6
D) Lower its temperature by a factor of 5.4

Question 54

A spaceship approaches Earth at 0.9 times the speed of light and shines a powerful searchlight onto Earth.How fast will the photons from this searchlight be moving when they hit Earth?

Question 55

Star A and star B appear equally bright in the sky.Star A is twice as far away from Earth as star B.How do the luminosities of stars A and B compare?

A) Star A is four times as luminous as star B.
B) Star A is twice as luminous as star B.
C) Star B is twice as luminous as star A.
D) Star B is four times as luminous as star A.

Question 56

What is the surface temperature of a star that has a peak wavelength of 290 nm?

A) 1,000 K
B) 2,000 K
C) 5,000 K
D) 10,000 K
E) 100,000 K

Question 57

Compare and contrast the wavelengths,frequencies,speeds,and energies of red and blue photons.

Question 58

Compare two blackbody objects,one at 200 K and one at 400 K.How much larger is the flux from the 400 K object,compared to the flux from the 200 K object?

A) Twice as much
B) Four times as much
C) Eight times as much
D) Sixteen times as much

Question 59

A black car left in the sunlight becomes hotter than a white car left in the sunlight under the same conditions because

A) the white car absorbs more sunlight than the black car.
B) the white car reflects more sunlight than the black car.
C) the black car absorbs only blue photons and reflects red photons,whereas the white car absorbs only red photons and reflects blue photons.
D) the atoms in the black car are smaller than the atoms in the white car.

Question 60

If Saturn has a semimajor axis of 10 AU and an albedo of 0.7,what is its expected temperature?

A) 130 K
B) 65 K
C) 35 K
D) 170 K

Question 61

Why do we see black lines in an absorption spectrum if the absorbed photons are (almost)instantaneously reemitted by the atoms in the cloud?

Question 62

How are atoms excited and why do they decay?

Question 63

For a star that lies in the plane of Earth's orbit around the Sun,how does the observed wavelength of the hydrogen absorption line at 656.28 nm in its spectrum change in wavelength (if at all)with the time of year?

Question 64

Star A emits a continuous spectrum of light that peaks at a wavelength of 450 nm.Star B emits a continuous spectrum of light that peaks at a wavelength of 700 nm.What is the ratio of the temperature of star A to star B if the emissions from both stars follow Wien's law?

Question 65

How much would you have to change the temperature of an object if you wanted to increase its flux by a factor of 100?

Question 66

If you were driving down a deserted country road and you saw a light in the distance,what would you need to measure or know about it in order to calculate how far away it was?

Question 67

If a street lamp at a distance of 100 meters from you is 10,000 times more luminous than a firefly,what is the distance the firefly has to be from you so it looks as bright as the street lamp at 100 meters?

Question 68

Suppose you observe a star emitting a certain emission line of helium at 584.8 nm.The rest wavelength of this line is 587.6 nm.How fast is the star moving? Is it moving toward you or away from you?

Question 69

What would you expect the temperature of a comet to be if its distance was 100 AU from the Sun? Assume that it is very icy and reflective so that its albedo is equal to 0.6.Does it matter what the radius of the comet is?

Question 70

What two factors control a planet's temperature?