Question 1

The average red giant is about 1,000 times more luminous than the average main-sequence star.If both kinds of stars have about the same brightness in our night sky, 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) 5.6 times farther
E) The red giants and main-sequence stars are approximately the same distance away.

Accepted Answer

The luminosity-distance relationship states that if two stars have the same apparent brightness, the one that is more luminous must be farther away. The distance is proportional to the square root of the luminosity ratio. Since red giants are 1,000 times more luminous, they are √1000 ≈ 32 times farther away.

Question 2

Describe, in your own words, why electrons cannot orbit the nucleus like the planets orbit the Sun.

Accepted Answer

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Question 3

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

Accepted Answer

The answer of Why do we see black lines in...

Question 4

Which of these planets would be expected to have the highest average temperature?
A) a light-colored planet close to its star
B) a dark-colored planet close to its star
C) a light-colored planet far from its star
D) a dark-colored planet far from its star
E) There is not enough information to know which would be the hottest.

Accepted Answer

A dark-colored planet close to its star would absorb more heat due to its color and proximity, leading to a higher average temperature.

Question 5

If a star has a peak wavelength of 290 nm, what is its surface temperature?
A) 1000 K
B) 2000 K
C) 5000 K
D) 10,000 K
E) 100,000 K

Accepted Answer

According to Wien's Law, the surface temperature of a star can be calculated using the formula: T = (2.9 x 10^6 nm K) / peak wavelength. For a peak wavelength of 290 nm, the temperature is approximately 10,000 K.

Question 6

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?

Accepted Answer

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Question 7

What different processes produce the patterns of light that can be viewed as: continuous spectra; emission spectra; and absorption spectra?

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Question 8

The difference in energy between the n = 2 and n =1 electronic energy levels in the hydrogen atom is 1.6 *10^-18 J.If an electron moves from the n = 1 level to the n=2 level, will a photon be emitted or absorbed? What will its energy be, and what type of electromagnetic radiation is it? Use the electromagnetic spectrum shown in the figure below to answer this question.

Accepted Answer

The answer of The difference in energy between the n...

Question 9

Star C and star D have the same luminosity.Star C is twice as far away from Earth as star D.How do the brightness levels 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.
E) Stars C and D appear equally bright.

Accepted Answer

The brightness of a star is inversely proportional to the square of its distance from the observer. Since star C is twice as far away as star D, it will appear 1/(2^2) = 1/4 as bright as star D. Thus, star D appears four times as bright as star C.

Question 10

If the Sun's luminosity were twice its actual value, Earth's temperature would
A) more than double.
B) double.
C) increase, but be less than double.
D) not be different.
E) decrease a small amount.

Accepted Answer

The temperature of Earth is related to the fourth root of the Sun's luminosity, so if the luminosity doubles, the temperature would increase, but not double.

Question 11

Compare the differences between a photon of red light and a photon of blue light.

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Question 12

At what peak wavelength does your body radiate the most given that your temperature is approximately that of Earth, which is 300 K? A) 10^-5 m B) 10^-3 m C) 10^-2 m D) 10 m E) 1,000 m

Accepted Answer

Wien's displacement law states that the peak wavelength of blackbody radiation is inversely proportional to its temperature. The formula is:$$\lambda_{max} = \frac{b}{T}$$where:$$\lambda_{max}$$ is the peak wavelength in metersb is Wien's displacement constant, which is 2.898 x 10^-3 m KT is the temperature in KelvinPlugging in the given temperature of 300 K, we get:$$\lambda_{max} = \frac{2.898 	imes 10^{-3} 	ext{ m K}}{300 	ext{ K}} = 9.66 	imes 10^{-6} 	ext{ m}$$This is closest to choice A, 10^-5 m.

Question 13

The first five energy levels of hydrogen are E₁ = 0 eV, E₂ = 10.2 eV, E₃ =12.1 eV, E₄ =12.7 eV, and E₅ = 13.1 eV.If the electron is in the n = 4 level, what energies can a single emitted photon have?

Accepted Answer

The answer of The first five energy levels of hydrogen...

Question 14

If a lightbulb is moved twice as far away, its luminosity will be
A) doubled.
B) quadrupled.
C) halved.
D) 1/4 the original.
E) the same.

Accepted Answer

The answer of If a lightbulb is moved twice as...

Question 15

How is the energy of a photon related to its frequency, wavelength, and speed?

Accepted Answer

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Question 16

How are atoms excited, and why do they become de-excited?

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Question 17

If Jupiter has a temperature of 165 K, at what wavelength does its spectrum peak? Use the electromagnetic spectrum in the figure below to answer this question. 
A) 18 nm-orange visible wavelengths
B) 1,800 mm-microwave wavelengths
C) 1,800 nm-infrared wavelengths
D) 18,000 nm-ultraviolet wavelengths
E) 18,000 nm-infrared wavelengths

Accepted Answer

The answer of If Jupiter has a temperature of 165...

Question 18

If the typical temperature of a red giant is 3000 K, at what wavelength is its radiation the brightest? Use the electromagnetic spectrum in the figure below to help you answer this question. 
A) 1 $\mu$m-infrared wavelengths
B) 1 $\mu$m-red visible wavelengths
C) 20$\mu$m-infrared wavelengths
D) 20 $\mu$m-red visible wavelengths
E) 700 $\mu$m-red visible wavelengths

Accepted Answer

The answer of If the typical temperature of a red...

Question 19

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 twice as luminous as star B.
B) Star B is twice as luminous as star A.
C) Star A is four times as luminous as star B.
D) Star B is four times as luminous as star A.
E) Stars A and B have the same luminosity.

Accepted Answer

The apparent brightness of a star is inversely proportional to the square of its distance. Since star A is twice as far as star B but appears equally bright, it must be four times more luminous to compensate for the increased distance.

Question 20

What is an electromagnetic wave?

Accepted Answer

The answer of What is an electromagnetic wave?...

Quiz 5: Light

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

Describe, in your own words, why electrons cannot orbit the nucleus like the planets orbit the Sun.

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

Which of these planets would be expected to have the highest average temperature?

If a star has a peak wavelength of 290 nm, what is its surface temperature?

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?

What different processes produce the patterns of light that can be viewed as: continuous spectra; emission spectra; and absorption spectra?

Star C and star D have the same luminosity.Star C is twice as far away from Earth as star D.How do the brightness levels of stars C and D compare?

If the Sun's luminosity were twice its actual value, Earth's temperature would

Compare the differences between a photon of red light and a photon of blue light.

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

The first five energy levels of hydrogen are E1 = 0 eV, E2 = 10.2 eV, E3 =12.1 eV, E4 =12.7 eV, and E5 = 13.1 eV.If the electron is in the n = 4 level, what energies can a single emitted photon have?

If a lightbulb is moved twice as far away, its luminosity will be

How is the energy of a photon related to its frequency, wavelength, and speed?

How are atoms excited, and why do they become de-excited?

If Jupiter has a temperature of 165 K, at what wavelength does its spectrum peak? Use the electromagnetic spectrum in the figure below to answer this question.

If the typical temperature of a red giant is 3000 K, at what wavelength is its radiation the brightest? Use the electromagnetic spectrum in the figure below to help you answer this question.

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?

What is an electromagnetic wave?

The first five energy levels of hydrogen are E₁ = 0 eV, E₂ = 10.2 eV, E₃ =12.1 eV, E₄ =12.7 eV, and E₅ = 13.1 eV.If the electron is in the n = 4 level, what energies can a single emitted photon have?