Modern Physics

As the temperature of a blackbody increases, what happens to the peak wavelength of the light it

radiates?

• It gets longer

• It gets shorter

• he wavelength is not affected by the temperature of the object.

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Two identical metal bars are heated up until they are both glowing. One of them is "red hot" and the

other is "blue hot." Which one is hotter, the one that glows red or the one that glows blue?

• the red one

• the blue one

• We cannot tell without knowing more about the two bars.

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A photon of blue light and a photon of red light are traveling in vacuum. The photon of blue light

• has a smaller wavelength than a photon of red light and travels with the same

• has a smaller wavelength than a photon of red light and travels with a greater speed.

• has a longer wavelength than a photon of red light and travels with the same speed.

• has a longer wavelength than a photon of red light and travels with a greater speed.

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Increasing the brightness of a beam of light without changing its color will increase

• the number of photons per second traveling in the beam.

• he energy of each photon

• he speed of the photons.

• the frequency of the light.

• the wavelength of the photons.

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If the wavelength of a photon is doubled, what happens to its energy?

• It is reduced to one-half of its original value.

• It stays the same.

• It is doubled

• It is increased to four times its original value.

• It is reduced to one-fourth of its original value.

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Light of a given wavelength is used to illuminate the surface of a metal, however, no photoelectrons are emitted. In order to cause electrons to be ejected from the surface of this metal you should ....

• use light of a longer wavelength.

• use light of a shorter wavelength

• use light of the same wavelength but increase its intensity

• use light of the same wavelength but decrease its intensity.

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A blue laser beam is incident on a metallic surface, causing electrons to be ejected from the metal. If

the frequency of the laser beam is increased while the intensity of the beam is held fixed

• the rate of ejected electrons will decrease and their maximum kinetic energy will increase

• the rate of ejected electrons will remain the same but their maximum kinetic energy will increase.

• the rate of ejected electrons will increase and their maximum kinetic energy will increase.

• he rate of ejected electrons will remain the same but their maximum kinetic energy will decrease.

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Monochromatic light falls on a metal surface and electrons are ejected. If the intensity of the light is increased, what will happen to the ejection rate and maximum energy of the electrons?

• greater rate; same maximum energy

• same rate; greater maximum energy

• greater rate; greater maximum energy.

• same rate; same maximum energy.

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When the surface of a metal is exposed to blue light, electrons are emitted. If the intensity of the blue light is increased, which of the following things will also increase?

• the number of electrons ejected per second

• the maximum kinetic energy of the ejected electrons

• the time lag between the onset of the absorption of light and the ejection of electrons

• the work function

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How much energy is carried by a photon of light having frequency 110 GHz? (h=6.626 x 10-34 J • s)

• 1.1 x 10-20 J

• 1.4 x 10-22 J

• 7.3 x 10-23 J

• 1.3 x 10-25 J

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