Question 1

If the surface of our bodies is at 37°C,at what wavelength does the radiation that we emit peak if we behave like a blackbody? The constant in Wien's law is 0.0029 m ∙ K.

Accepted Answer

The answer of If the surface of our bodies is...

Question 2

Each photon in a beam of light has an energy of 4.20 eV.What is the wavelength of this light? (c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s,1 eV = 1.60 × 10-19 J)

Accepted Answer

A) 321 nm 
B) 103 nm 
C) 296 nm 
D) 412 nm 
E) 420 nm 
A) 321 nm 
B) 103 nm 
C) 296 nm 
D) 412 nm 
E) 420 nm

Question 3

When light of wavelength 350 nm is incident on a metal surface,the stopping potential of the photoelectrons is 0.500 V.What is the threshold (cutoff)frequency of this metal? (c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s,1 eV = 1.60 × 10-19 J)

Accepted Answer

A) 3.47 × 1014 Hz 
B) 3.74 × 1014 Hz 
C) 4.73 × 1014 Hz 
D) 7.36 × 1014 Hz 
A) 3.47 × 1014 Hz 
B) 3.74 × 1014 Hz 
C) 4.73 × 1014 Hz 
D) 7.36 × 1014 Hz

Question 4

A beam of light with a frequency range from 3.01 × 1014 Hz to 6.10 × 1014 Hz is incident on a metal surface.If the work function of the metal surface is 2.20 eV,what is the maximum kinetic energy of photoelectrons ejected from this surface? (h = 6.626 × 10-34 J ∙ s,1 eV = 1.60 × 10-19 J)

Accepted Answer

A) 0.33 eV 
B) 0.21 eV 
C) 0.42 eV 
D) 0.16 eV 
E) 0.48 eV 
A) 0.33 eV 
B) 0.21 eV 
C) 0.42 eV 
D) 0.16 eV 
E) 0.48 eV

Question 5

A sphere of surface area 1.25 m2 and emissivity 1.0 is at a temperature of 100°C.At what rate does it radiate energy into empty space? (σ = 5.67 × 10-8 W/m2 ∙ K4)

Accepted Answer

A) 7.1 W 
B) 0.71 mW 
C) 1.4 kW 
D) 9.9 mW 
E) 3.7 W 
A) 7.1 W 
B) 0.71 mW 
C) 1.4 kW 
D) 9.9 mW 
E) 3.7 W

Question 6

A certain photon,after being scattered from a free electron that was at rest,moves at an angle of 120° with respect to the incident direction.If the wavelength of the incident photon is 0.6110 nm,what is the kinetic energy of the recoiling electron? (melectron = 9.11 × 10-31 kg,c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s)

Accepted Answer

A) 1.5 × 10-18 J 
B) 1.9 × 10-18 J 
C) 3.1 × 10-18 J 
D) 4.3 × 10-18 J 
E) 5.2 × 10-18 J 
A) 1.5 × 10-18 J 
B) 1.9 × 10-18 J 
C) 3.1 × 10-18 J 
D) 4.3 × 10-18 J 
E) 5.2 × 10-18 J

Question 7

A photocathode having a work function of 2.4 eV is illuminated with monochromatic light whose photon energy is 3.4 eV.What is maximum kinetic energy of the photoelectrons produced?(c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s,1 eV = 1.60 × 10-19 J)

Accepted Answer

A) 1.6 × 10-19 J 
B) 3.8 × 10-19 J 
C) 4.4 × 10-19 J 
D) 4.9 × 10-19 J 
E) 5.4 × 10-19 J 
A) 1.6 × 10-19 J 
B) 3.8 × 10-19 J 
C) 4.4 × 10-19 J 
D) 4.9 × 10-19 J 
E) 5.4 × 10-19 J

Question 8

An 84-kW AM radio station broadcasts at 1000 kHz.How many photons are emitted each second by the transmitting antenna? (h = 6.626 × 10-34 J ∙ s)

Accepted Answer

A) 1.3 × $10^{32}$ 
B) 2.9 × $10^{24}$ 
C) 6.3 × $10^{12}$ 
D) 1.4 × $10^{15}$ 
A) 1.3 × $10^{32}$ 
B) 2.9 × $10^{24}$ 
C) 6.3 × $10^{12}$ 
D) 1.4 × $10^{15}$

Question 9

What is the longest wavelength of light that can cause photoelectron emission from a metal that has a work function of 2.20 eV? (1 eV = 1.60 × 10-19 J,c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s)

Accepted Answer

A) 417 nm 
B) 257 nm 
C) 344 nm 
D) 565 nm 
E) 610 nm 
A) 417 nm 
B) 257 nm 
C) 344 nm 
D) 565 nm 
E) 610 nm

Question 10

Monochromatic light is incident on a metal surface,and the ejected electrons give rise to a current in the circuit shown in the figure.The maximum kinetic energy of the ejected electrons is determined by applying a reverse ('stopping')potential,sufficient to reduce the current in the ammeter to zero.If the intensity of the incident light is increased,how will the required stopping potential change?

Accepted Answer

A) It will remain unchanged. 
B) It will increase. 
C) It will decrease. 
A) It will remain unchanged. 
B) It will increase. 
C) It will decrease.

Question 11

At what rate are photons emitted by a 50.0-W sodium vapor lamp if it is producing monochromatic light of wavelength 589 nm? (c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s)

Accepted Answer

1.48 × 10²⁰

Question 12

If the work function of a metal surface is 2.20 eV,what frequency of incident light would give a maximum kinetic energy of 0.25 eV to the photoelectrons ejected from this surface? (1 eV = 1.60 × 10-19 J, h = 6.626 × 10-34 J ∙ s)

Accepted Answer

A) 2.05 × 1014 Hz 
B) 1.02 × 1014 Hz 
C) 2.50 × 1014 Hz 
D) 3.53 × 1014 Hz 
E) 5.92 × 1014 Hz 
A) 2.05 × 1014 Hz 
B) 1.02 × 1014 Hz 
C) 2.50 × 1014 Hz 
D) 3.53 × 1014 Hz 
E) 5.92 × 1014 Hz

Question 13

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?

Accepted Answer

A) the red one 
B) the blue one 
C) We cannot tell without knowing more about the two bars. 
A) the red one 
B) the blue one 
C) We cannot tell without knowing more about the two bars.

Question 14

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

Accepted Answer

A) 1.1 × 10-20 J 
B) 1.4 × 10-22 J 
C) 7.3 × 10-23 J 
D) 1.3 × 10-25 J 
A) 1.1 × 10-20 J 
B) 1.4 × 10-22 J 
C) 7.3 × 10-23 J 
D) 1.3 × 10-25 J

Question 15

If the sunlight from a star peaks at a wavelength of 0.55 µm,what temperature does this imply for the surface of that star? The constant in Wien's law is 0.00290 m ∙ K.

Accepted Answer

A) 9500 K 
B) 5300 K 
C) 2500 K 
D) 25,000 K 
E) 15,000 K 
A) 9500 K 
B) 5300 K 
C) 2500 K 
D) 25,000 K 
E) 15,000 K

Question 16

What is the wavelength of a photon having the same momentum as an electron that is traveling at 7.5 km/s? (h = 6.626 × 10-34 J ∙ s,melectron = 9.11 × 10-31 kg)

Accepted Answer

Question 17

Light with a wavelength of 310 nm is incident on a metal that has a work function of 3.80 eV.What is the maximum kinetic energy that a photoelectron ejected in this process can have? (1 eV = 1.60 × 10-19 J,c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s)

Accepted Answer

A) 0.62 × 10-19 J 
B) 0.21 × 10-19 J 
C) 0.36 × 10-19 J 
D) 0.48 × 10-19 J 
E) 0.33 × 10-19 J 
A) 0.62 × 10-19 J 
B) 0.21 × 10-19 J 
C) 0.36 × 10-19 J 
D) 0.48 × 10-19 J 
E) 0.33 × 10-19 J

Question 18

For a certain metal,light of frequency 7.24 × 10-14 Hz is just barely able to dislodge photoelectrons from the metal.(h = 6.626 × 10-34 J ∙ s, 1 eV = 1.60 × 10-19 J,e = 1.60 × 10-19
C)
(a)What will be the stopping potential if light of frequency 8.75 × 10-14 Hz is shone on the metal?
(b)What is the work function (in electron-volts)of this metal?

Accepted Answer

(a)0.625 V

Question 19

Two sources emit beams of light of wavelength 550 nm.The light from source A has an intensity of 10 µW/m2,and the light from source B has an intensity of 20 µW/m2.This is all we know about the two beams.Which of the following statements about these beams are correct? (There could be more than one correct choice.)

Accepted Answer

A) Beam B carries twice as many photons per second as beam A. 
B) A photon in beam B has twice the energy of a photon in beam A. 
C) The frequency of the light in beam B is twice as great as the frequency of the light in beam A. 
D) A photon in beam B has the same energy as a photon in beam A. 
E) None of the above statements are true. 
A) Beam B carries twice as many photons per second as beam A. 
B) A photon in beam B has twice the energy of a photon in beam A. 
C) The frequency of the light in beam B is twice as great as the frequency of the light in beam A. 
D) A photon in beam B has the same energy as a photon in beam A. 
E) None of the above statements are true.

Question 20

If the longest wavelength of light that is able to dislodge electrons from a metal is 373 nm,what is the work function of that metal,in electron-volts? (1 eV = 1.60 × 10-19 J,c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s)

Accepted Answer

Exam 27: Quantum Optics

If the surface of our bodies is at 37°C,at what wavelength does the radiation that we emit peak if we behave like a blackbody? The constant in Wien's law is 0.0029 m ∙ K.

Each photon in a beam of light has an energy of 4.20 eV.What is the wavelength of this light? (c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s,1 eV = 1.60 × 10-19 J)

When light of wavelength 350 nm is incident on a metal surface,the stopping potential of the photoelectrons is 0.500 V.What is the threshold (cutoff)frequency of this metal? (c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s,1 eV = 1.60 × 10-19 J)

A beam of light with a frequency range from 3.01 × 1014 Hz to 6.10 × 1014 Hz is incident on a metal surface.If the work function of the metal surface is 2.20 eV,what is the maximum kinetic energy of photoelectrons ejected from this surface? (h = 6.626 × 10-34 J ∙ s,1 eV = 1.60 × 10-19 J)

A sphere of surface area 1.25 m2 and emissivity 1.0 is at a temperature of 100°C.At what rate does it radiate energy into empty space? (σ = 5.67 × 10-8 W/m2 ∙ K4)

A photocathode having a work function of 2.4 eV is illuminated with monochromatic light whose photon energy is 3.4 eV.What is maximum kinetic energy of the photoelectrons produced?(c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s,1 eV = 1.60 × 10-19 J)

An 84-kW AM radio station broadcasts at 1000 kHz.How many photons are emitted each second by the transmitting antenna? (h = 6.626 × 10-34 J ∙ s)

What is the longest wavelength of light that can cause photoelectron emission from a metal that has a work function of 2.20 eV? (1 eV = 1.60 × 10-19 J,c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s)

At what rate are photons emitted by a 50.0-W sodium vapor lamp if it is producing monochromatic light of wavelength 589 nm? (c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s)

If the work function of a metal surface is 2.20 eV,what frequency of incident light would give a maximum kinetic energy of 0.25 eV to the photoelectrons ejected from this surface? (1 eV = 1.60 × 10-19 J, h = 6.626 × 10-34 J ∙ s)

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?

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

If the sunlight from a star peaks at a wavelength of 0.55 µm,what temperature does this imply for the surface of that star? The constant in Wien's law is 0.00290 m ∙ K.

What is the wavelength of a photon having the same momentum as an electron that is traveling at 7.5 km/s? (h = 6.626 × 10-34 J ∙ s,melectron = 9.11 × 10-31 kg)

Light with a wavelength of 310 nm is incident on a metal that has a work function of 3.80 eV.What is the maximum kinetic energy that a photoelectron ejected in this process can have? (1 eV = 1.60 × 10-19 J,c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s)

If the longest wavelength of light that is able to dislodge electrons from a metal is 373 nm,what is the work function of that metal,in electron-volts? (1 eV = 1.60 × 10-19 J,c = 3.00 × 108 m/s,h = 6.626 × 10-34 J ∙ s)

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Each photon in a beam of light has an energy of 4.20 eV.What is the wavelength of this light? (c = 3.00 × 10⁸ m/s,h = 6.626 × 10^-34 J ∙ s,1 eV = 1.60 × 10^-19 J)

When light of wavelength 350 nm is incident on a metal surface,the stopping potential of the photoelectrons is 0.500 V.What is the threshold (cutoff)frequency of this metal? (c = 3.00 × 10⁸ m/s,h = 6.626 × 10^-34 J ∙ s,1 eV = 1.60 × 10^-19 J)

A sphere of surface area 1.25 m² and emissivity 1.0 is at a temperature of 100°C.At what rate does it radiate energy into empty space? (σ = 5.67 × 10^-8 W/m² ∙ K⁴)

A photocathode having a work function of 2.4 eV is illuminated with monochromatic light whose photon energy is 3.4 eV.What is maximum kinetic energy of the photoelectrons produced?(c = 3.00 × 10⁸ m/s,h = 6.626 × 10^-34 J ∙ s,1 eV = 1.60 × 10^-19 J)

An 84-kW AM radio station broadcasts at 1000 kHz.How many photons are emitted each second by the transmitting antenna? (h = 6.626 × 10^-34 J ∙ s)

What is the longest wavelength of light that can cause photoelectron emission from a metal that has a work function of 2.20 eV? (1 eV = 1.60 × 10^-19 J,c = 3.00 × 10⁸ m/s,h = 6.626 × 10^-34 J ∙ s)

At what rate are photons emitted by a 50.0-W sodium vapor lamp if it is producing monochromatic light of wavelength 589 nm? (c = 3.00 × 10⁸ m/s,h = 6.626 × 10^-34 J ∙ s)

If the work function of a metal surface is 2.20 eV,what frequency of incident light would give a maximum kinetic energy of 0.25 eV to the photoelectrons ejected from this surface? (1 eV = 1.60 × 10^-19 J, h = 6.626 × 10^-34 J ∙ s)

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

What is the wavelength of a photon having the same momentum as an electron that is traveling at 7.5 km/s? (h = 6.626 × 10^-34 J ∙ s,m_electron = 9.11 × 10^-31 kg)

Light with a wavelength of 310 nm is incident on a metal that has a work function of 3.80 eV.What is the maximum kinetic energy that a photoelectron ejected in this process can have? (1 eV = 1.60 × 10^-19 J,c = 3.00 × 10⁸ m/s,h = 6.626 × 10^-34 J ∙ s)

If the longest wavelength of light that is able to dislodge electrons from a metal is 373 nm,what is the work function of that metal,in electron-volts? (1 eV = 1.60 × 10^-19 J,c = 3.00 × 10⁸ m/s,h = 6.626 × 10^-34 J ∙ s)