Question 1

The maximum kinetic energy of photoelectrons from a metal is equal to the work function of that metal.

Accepted Answer

The maximum kinetic energy of photoelectrons from a metal is equal to the difference between the energy of the incident photon and the work function of that metal. This is known as the photoelectric effect.

Question 2

An electron and a proton move at the same speed.Which has a longer de-Broglie wavelength?
A)the electron
B)the proton
C)Both particles have the same wavelength.
D)Since electrons and protons are particles,it is meaningless to discuss a wavelength associated with these particles.

Accepted Answer

According to de-Broglie hypothesis, the wavelength of a particle is inversely proportional to its momentum. As both electron and proton are moving at the same speed, the proton will have a higher momentum compared to the electron due to its higher mass. Therefore, the de-Broglie wavelength of the proton will be shorter than that of the electron. Hence, the electron has a longer de-Broglie wavelength.

Question 3

A photon of violet light has more energy than a photon of green light.

Accepted Answer

This statement is true. Violet light has a shorter wavelength and higher frequency than green light, thus each photon of violet light contains more energy than a photon of green light.

Question 4

A beam of light having frequency greater than the threshold frequency shines on a metal surface.By increasing the intensity of this light,you increase the number of photoelectrons emitted per second from this metal.

Accepted Answer

According to the photoelectric effect, the intensity of light determines the number of photons incident on the metal surface, but it does not affect the energy of individual photons. So, by increasing the intensity, the number of photoelectrons emitted per second increases, but not their individual energies.

Question 5

Monochromatic light is incident on a metal surface.The ejected electrons give rise to a current in the circuit shown.The maximum 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?
A)It will remain unchanged.
B)It will increase.
C)It will decrease.

Accepted Answer

The stopping potential is determined by the maximum energy of the ejected electrons. Increasing the intensity of the incident light will only increase the number of electrons ejected, but not their maximum energy. Therefore, the stopping potential will remain unchanged.

Question 6

A photon collides with an electron that is initially at rest,causing the electron to move.After the collision,the wavelength of the photon is
A)greater than its initial value.
B)equal to its initial value.
C)less than its initial value.

Accepted Answer

The collision described is an example of Compton scattering, where a photon collides with a stationary electron. In this process, the photon transfers some of its energy to the electron, resulting in an increase in the photon's wavelength (a decrease in energy). Thus, the wavelength of the photon after the collision is greater than its initial value.

Question 7

A friend in your physics class tells you that illuminating a surface with any laser will result in the emission of photoelectrons,as long as the illumination lasts long enough to supply the needed energy.Is she correct? Support your answer.

Accepted Answer

The answer of A friend in your physics class tells...

Question 8

When light is absorbed by a metal,the energy of each light quantum is usually given to several adjacent electrons.

Accepted Answer

When light is absorbed by a metal, the energy of each light quantum (photon) is typically given to a single electron, which can result in the photoelectric effect.

Question 9

A photon of blue light
A)has a smaller wavelength than a photon of red light and travels with the same speed.
B)has a smaller wavelength than a photon of red light and travels with a greater speed.
C)has a longer wavelength than a photon of red light and travels with the same speed.
D)has a longer wavelength than a photon of red light and travels with a greater speed.

Accepted Answer

The wavelength of blue light is shorter than that of red light, as blue light has a higher frequency. However, both colors of light travel at the same speed in a vacuum, which is the speed of light (c). Therefore, option A is the correct answer.

Question 10

A beam of light having frequency greater than the threshold frequency shines on a metal surface.By increasing the frequency of this light,you increase the number of photoelectrons emitted per second from this metal.

Accepted Answer

Increasing the frequency of light above the threshold frequency increases the kinetic energy of the emitted photoelectrons, not their number. The number of photoelectrons depends on the intensity of the light.

Question 11

Illuminating a particular metal surface with a helium-neon laser results in the emission of photoelectrons.Will the kinetic energy of the photoelectrons increase if you increase the laser's power? Support your answer.

Accepted Answer

The answer of Illuminating a particular metal surface with a...

Question 12

To say that a particle's energy is "quantized" means that it can have only certain discrete values.

Accepted Answer

A particle's energy can only exist in certain levels or "quanta" due to the quantization of energy in quantum mechanics.

Question 13

A quantum of blue light carries more energy than a quantum of red light.

Accepted Answer

The energy of a photon (quantum of light) is directly proportional to its frequency. Blue light has a higher frequency than red light, so each photon of blue light carries more energy than a photon of red light.

Question 14

If there are two photons with different energies,the one that has a higher energy
A)has the higher frequency.
B)has the higher wavelength.
C)has the higher velocity.
D)Two of the above are valid.

Accepted Answer

The energy of a photon is directly proportional to its frequency, as given by the equation E = hf, where E is energy, h is Planck's constant, and f is frequency. Therefore, the photon with higher energy must have a higher frequency.

Question 15

If the threshold frequency of a certain metal is 2.0 × 10¹⁴ Hz,light of frequency 1.9 x 10¹⁴ Hz will not be able to dislodge any photoelectrons from this metal.

Accepted Answer

The frequency of the incident light is less than the threshold frequency, so it does not have enough energy to dislodge photoelectrons.

Question 16

Electrons are sent through a double-slit apparatus,and an interference pattern is observed.If protons are sent through the same apparatus with the same speed as that of the electrons,the distance between the fringes would be
A)closer together.
B)farther apart.
C)the same as that of the electrons since the velocities are the same.

Accepted Answer

The distance between the fringes in an interference pattern is dependent on the wavelength of the particles passing through the double-slit apparatus. Electrons have a very small de Broglie wavelength, which means the distance between the fringes is relatively large. Protons, on the other hand, have a much larger de Broglie wavelength due to their higher mass. This means that the distance between the fringes will be smaller, and they will be closer together.

Question 17

We do not observe the wave behavior of particles of matter in our daily lives because their de Broglie wavelengths are too small for their wave nature to show up.

Accepted Answer

According to the de Broglie equation, the wavelength of a particle is inversely proportional to its momentum, so everyday objects have extremely small wavelengths due to their low velocities. As a result, their wave nature is not noticeable in our daily lives.

Question 18

An electron is contrained to be inside a one-dimensional box.If the length of the box is doubled,the minimum energy of the electron
A)decreases by a factor of four.
B)decreases by a factor of two.
C)does not change.
D)is zero,regardless of the the size of the box.

Accepted Answer

The minimum energy of an electron in a one-dimensional box is inversely proportional to the square of the length of the box. Doubling the length decreases the energy by a factor of four.

Question 19

Typical photoelectric work functions are in the range of a few joules.

Accepted Answer

Typical photoelectric work functions are in the range of a few electronvolts (eV), not joules.

Question 20

The threshold frequency of a metal is the largest frequency of light that will dislodge photoelectrons from this metal.

Accepted Answer

The threshold frequency is the minimum frequency of light required to dislodge photoelectrons from a metal, not the largest.

Quiz 28: Quantum Physics

The maximum kinetic energy of photoelectrons from a metal is equal to the work function of that metal.

An electron and a proton move at the same speed.Which has a longer de-Broglie wavelength?

A photon of violet light has more energy than a photon of green light.

A beam of light having frequency greater than the threshold frequency shines on a metal surface.By increasing the intensity of this light,you increase the number of photoelectrons emitted per second from this metal.

A photon collides with an electron that is initially at rest,causing the electron to move.After the collision,the wavelength of the photon is

A friend in your physics class tells you that illuminating a surface with any laser will result in the emission of photoelectrons,as long as the illumination lasts long enough to supply the needed energy.Is she correct? Support your answer.

When light is absorbed by a metal,the energy of each light quantum is usually given to several adjacent electrons.

A photon of blue light

A beam of light having frequency greater than the threshold frequency shines on a metal surface.By increasing the frequency of this light,you increase the number of photoelectrons emitted per second from this metal.

Illuminating a particular metal surface with a helium-neon laser results in the emission of photoelectrons.Will the kinetic energy of the photoelectrons increase if you increase the laser's power? Support your answer.

To say that a particle's energy is "quantized" means that it can have only certain discrete values.

A quantum of blue light carries more energy than a quantum of red light.

If there are two photons with different energies,the one that has a higher energy

If the threshold frequency of a certain metal is 2.0 × 1014 Hz,light of frequency 1.9 x 1014 Hz will not be able to dislodge any photoelectrons from this metal.

Electrons are sent through a double-slit apparatus,and an interference pattern is observed.If protons are sent through the same apparatus with the same speed as that of the electrons,the distance between the fringes would be

We do not observe the wave behavior of particles of matter in our daily lives because their de Broglie wavelengths are too small for their wave nature to show up.

An electron is contrained to be inside a one-dimensional box.If the length of the box is doubled,the minimum energy of the electron

Typical photoelectric work functions are in the range of a few joules.

The threshold frequency of a metal is the largest frequency of light that will dislodge photoelectrons from this metal.

If the threshold frequency of a certain metal is 2.0 × 10¹⁴ Hz,light of frequency 1.9 x 10¹⁴ Hz will not be able to dislodge any photoelectrons from this metal.