Dual nature of radiation and matter mcq with answers
Time Left: 45:00
Total Marks: 140, Obtained Marks: 0
1. What is the work function of a metal?
A. The energy required to ionize an electron within the metal
B. The minimum energy required for an electron to escape from the metal surface
C. The energy required to create free electrons within the metal
D. The energy needed to overcome thermal resistance in a metal
The correct answer is B. The minimum energy required for an electron to escape from the metal surface.
Explanation:
The work function is the minimum energy required to overcome the attractive forces holding an electron within the metal, allowing it to escape from the surface.
Explanation:
The work function is the minimum energy required to overcome the attractive forces holding an electron within the metal, allowing it to escape from the surface.
2. In thermionic emission, electrons are emitted from a metal by providing:
A. Light energy of a suitable frequency
B. High voltage electric field
C. Sufficient thermal energy
D. Mechanical force
The correct answer is C. Sufficient thermal energy.
Explanation:
In thermionic emission, heating the metal provides sufficient thermal energy to the electrons to escape the surface.
Explanation:
In thermionic emission, heating the metal provides sufficient thermal energy to the electrons to escape the surface.
3. Which of the following is NOT a method for electron emission from a metal surface?
A. Thermionic emission
B. Photoelectric emission
C. Field emission
D. Electrolytic emission
The correct answer is D. Electrolytic emission.
Explanation:
Electron emission from a metal can occur via thermionic, photoelectric, or field emission, but not through electrolytic processes.
Explanation:
Electron emission from a metal can occur via thermionic, photoelectric, or field emission, but not through electrolytic processes.
4. The unit of the work function of a metal is commonly measured in:
A. Joules
B. Volts
C. Coulombs
D. Electron Volts (eV)
The correct answer is D. Electron Volts (eV).
Explanation:
The work function is measured in electron volts (eV), which represents the energy gained by an electron when accelerated through a potential difference of 1 volt.
Explanation:
The work function is measured in electron volts (eV), which represents the energy gained by an electron when accelerated through a potential difference of 1 volt.
5. Who discovered the phenomenon of photoelectric emission?
A. Wilhelm Hallwachs
B. Heinrich Hertz
C. Philipp Lenard
D. Albert Einstein
The correct answer is B. Heinrich Hertz.
Explanation:
Heinrich Hertz discovered photoelectric emission in 1887 while observing that ultraviolet light increased the intensity of sparks in his experiments.
Explanation:
Heinrich Hertz discovered photoelectric emission in 1887 while observing that ultraviolet light increased the intensity of sparks in his experiments.
6. Which of the following factors directly affects the photoelectric current in a photoelectric effect experiment?
A. Frequency of the incident light
B. Intensity of the incident light
C. Threshold frequency of the metal
D. Stopping potential
The correct answer is B. Intensity of the incident light.
Explanation:
The photoelectric current is directly proportional to the intensity of the incident light. A higher intensity means more photons striking the photosensitive plate per second, causing more electrons to be emitted and thereby increasing the photoelectric current.
Explanation:
The photoelectric current is directly proportional to the intensity of the incident light. A higher intensity means more photons striking the photosensitive plate per second, causing more electrons to be emitted and thereby increasing the photoelectric current.
7. In a photoelectric effect experiment, if the frequency of the incident radiation is increased (above the threshold frequency) while keeping the intensity constant, what happens to the stopping potential?
A. It increases
B. It decreases
C. It remains the same
D. It becomes zero
The correct answer is A. It increases.
Explanation:
The stopping potential increases with the frequency of the incident radiation. This is because a higher frequency means photons with more energy, which gives the emitted electrons higher kinetic energy. As a result, a greater retarding potential (stopping potential) is needed to stop them.
Explanation:
The stopping potential increases with the frequency of the incident radiation. This is because a higher frequency means photons with more energy, which gives the emitted electrons higher kinetic energy. As a result, a greater retarding potential (stopping potential) is needed to stop them.
8. What does the threshold frequency represent in a photoelectric effect experiment?
A. The frequency below which no photoelectric emission occurs
B. The minimum frequency required to achieve saturation current
C. The frequency at which photoelectric emission is maximum
D. The frequency at which the stopping potential is zero
The correct answer is A. The frequency below which no photoelectric emission occurs.
Explanation:
The threshold frequency is the minimum frequency of incident light required to cause photoelectric emission from a given material. Below this frequency, no photoelectrons are emitted, regardless of the intensity of the light.
Explanation:
The threshold frequency is the minimum frequency of incident light required to cause photoelectric emission from a given material. Below this frequency, no photoelectrons are emitted, regardless of the intensity of the light.
9. What effect does increasing the intensity of incident light have on the stopping potential in a photoelectric effect experiment?
A. Increases the stopping potential
B. Decreases the stopping potential
C. Has no effect on the stopping potential
D. Increases the threshold frequency
The correct answer is C. Has no effect on the stopping potential.
Explanation:
The stopping potential is independent of the intensity of incident light. It only depends on the frequency of the light, as the maximum kinetic energy of the emitted electrons is related to the energy of each photon, which is frequency-dependent.
Explanation:
The stopping potential is independent of the intensity of incident light. It only depends on the frequency of the light, as the maximum kinetic energy of the emitted electrons is related to the energy of each photon, which is frequency-dependent.
10. Why does the photoelectric emission start instantaneously, even for low-intensity light, as long as the frequency is above the threshold?
A. Because the energy of photons is independent of intensity
B. Due to the threshold frequency being exceeded
C. Both A and B
D. None of the above
The correct answer is C. Both A and B.
Explanation:
The photoelectric emission is an instantaneous process because, as long as the incident light has a frequency above the threshold, each photon has sufficient energy to eject an electron immediately upon contact. Intensity affects the number of electrons emitted per second but not the delay in emission.
Explanation:
The photoelectric emission is an instantaneous process because, as long as the incident light has a frequency above the threshold, each photon has sufficient energy to eject an electron immediately upon contact. Intensity affects the number of electrons emitted per second but not the delay in emission.
11. Which of the following factors directly affects the photoelectric current in a photoelectric effect experiment?
A. Frequency of the incident light
B. Intensity of the incident light
C. Threshold frequency of the metal
D. Stopping potential
The correct answer is B. Intensity of the incident light.
Explanation:
The photoelectric current is directly proportional to the intensity of the incident light. A higher intensity means more photons striking the photosensitive plate per second, causing more electrons to be emitted and thereby increasing the photoelectric current.
Explanation:
The photoelectric current is directly proportional to the intensity of the incident light. A higher intensity means more photons striking the photosensitive plate per second, causing more electrons to be emitted and thereby increasing the photoelectric current.
12. In a photoelectric effect experiment, if the frequency of the incident radiation is increased (above the threshold frequency) while keeping the intensity constant, what happens to the stopping potential?
A. It increases
B. It decreases
C. It remains the same
D. It becomes zero
The correct answer is A. It increases.
Explanation:
The stopping potential increases with the frequency of the incident radiation. This is because a higher frequency means photons with more energy, which gives the emitted electrons higher kinetic energy. As a result, a greater retarding potential (stopping potential) is needed to stop them.
Explanation:
The stopping potential increases with the frequency of the incident radiation. This is because a higher frequency means photons with more energy, which gives the emitted electrons higher kinetic energy. As a result, a greater retarding potential (stopping potential) is needed to stop them.
13. What does the threshold frequency represent in a photoelectric effect experiment?
A. The frequency below which no photoelectric emission occurs
B. The minimum frequency required to achieve saturation current
C. The frequency at which photoelectric emission is maximum
D. The frequency at which the stopping potential is zero
The correct answer is A. The frequency below which no photoelectric emission occurs.
Explanation:
The threshold frequency is the minimum frequency of incident light required to cause photoelectric emission from a given material. Below this frequency, no photoelectrons are emitted, regardless of the intensity of the light.
Explanation:
The threshold frequency is the minimum frequency of incident light required to cause photoelectric emission from a given material. Below this frequency, no photoelectrons are emitted, regardless of the intensity of the light.
14. What effect does increasing the intensity of incident light have on the stopping potential in a photoelectric effect experiment?
A. Increases the stopping potential
B. Decreases the stopping potential
C. Has no effect on the stopping potential
D. Increases the threshold frequency
The correct answer is C. Has no effect on the stopping potential.
Explanation:
The stopping potential is independent of the intensity of incident light. It only depends on the frequency of the light, as the maximum kinetic energy of the emitted electrons is related to the energy of each photon, which is frequency-dependent.
Explanation:
The stopping potential is independent of the intensity of incident light. It only depends on the frequency of the light, as the maximum kinetic energy of the emitted electrons is related to the energy of each photon, which is frequency-dependent.
15. Why does the photoelectric emission start instantaneously, even for low-intensity light, as long as the frequency is above the threshold?
A. Because the energy of photons is independent of intensity
B. Due to the threshold frequency being exceeded
C. Both A and B
D. None of the above
The correct answer is C. Both A and B.
Explanation:
The photoelectric emission is an instantaneous process because, as long as the incident light has a frequency above the threshold, each photon has sufficient energy to eject an electron immediately upon contact. Intensity affects the number of electrons emitted per second but not the delay in emission.
Explanation:
The photoelectric emission is an instantaneous process because, as long as the incident light has a frequency above the threshold, each photon has sufficient energy to eject an electron immediately upon contact. Intensity affects the number of electrons emitted per second but not the delay in emission.
16. Which phenomenon could NOT be explained by the wave theory of light?
A. Diffraction
B. Photoelectric effect
C. Interference
D. Polarization
The correct answer is B. Photoelectric effect.
Explanation:
The wave theory of light could explain phenomena such as diffraction, interference, and polarization, but it could not account for the photoelectric effect, which requires the particle nature of light as described by Einstein’s quantum theory.
Explanation:
The wave theory of light could explain phenomena such as diffraction, interference, and polarization, but it could not account for the photoelectric effect, which requires the particle nature of light as described by Einstein’s quantum theory.
17. According to the wave theory of light, which of the following statements about photoelectric emission is expected but contradicts actual observations?
A. Emission is independent of light frequency.
B. Higher intensity results in higher energy absorbed by electrons.
C. Emission is instantaneous.
D. A threshold frequency for emission should exist.
The correct answer is B. Higher intensity results in higher energy absorbed by electrons.
Explanation:
According to wave theory, an electron should absorb energy continuously from light, leading to the expectation that greater intensity would increase electron energy. However, actual observations show that photoelectron energy depends on light frequency, not intensity.
Explanation:
According to wave theory, an electron should absorb energy continuously from light, leading to the expectation that greater intensity would increase electron energy. However, actual observations show that photoelectron energy depends on light frequency, not intensity.
18. Einstein’s photoelectric equation shows that the maximum kinetic energy of emitted photoelectrons depends on:
A. The intensity of incident radiation
B. The frequency of incident radiation
C. The number of electrons in the metal
D. The type of metal used
The correct answer is B. The frequency of incident radiation.
Explanation:
Einstein's equation \( K_{\text{max}} = h \nu - \phi_0 \) indicates that the maximum kinetic energy \( K_{\text{max}} \) of photoelectrons depends directly on the frequency \( \nu \) of the incident light and not on its intensity.
Explanation:
Einstein's equation \( K_{\text{max}} = h \nu - \phi_0 \) indicates that the maximum kinetic energy \( K_{\text{max}} \) of photoelectrons depends directly on the frequency \( \nu \) of the incident light and not on its intensity.
19. What does the threshold frequency \( \nu_0 \) in photoelectric effect represent?
A. The minimum frequency required to cause photoelectric emission
B. The maximum frequency that a metal can absorb
C. The intensity of the incident light
D. The work function of the metal
The correct answer is A. The minimum frequency required to cause photoelectric emission.
Explanation:
Threshold frequency \( \nu_0 \) is the minimum frequency below which no photoelectrons are emitted, regardless of the light intensity.
Explanation:
Threshold frequency \( \nu_0 \) is the minimum frequency below which no photoelectrons are emitted, regardless of the light intensity.
20. In Einstein’s model of photoelectric effect, which of the following best explains why photoelectric emission is instantaneous?
A. Electrons continuously absorb wave energy.
B. Absorption of a single photon releases an electron immediately.
C. High intensity light is required to release electrons.
D. Electrons are emitted with zero kinetic energy.
The correct answer is B. Absorption of a single photon releases an electron immediately.
Explanation:
Einstein proposed that photoelectric emission occurs through the absorption of individual light quanta (photons), allowing electrons to be emitted without delay as soon as they absorb enough energy.
Explanation:
Einstein proposed that photoelectric emission occurs through the absorption of individual light quanta (photons), allowing electrons to be emitted without delay as soon as they absorb enough energy.
21. According to Einstein’s photoelectric equation, if the frequency of incident light is doubled while keeping intensity constant, which of the following changes in the emitted photoelectrons is expected?
A. The number of emitted photoelectrons doubles.
B. The kinetic energy of each photoelectron remains constant.
C. The maximum kinetic energy of the photoelectrons increases.
D. The work function of the metal doubles.
The correct answer is C. The maximum kinetic energy of the photoelectrons increases.
Explanation:
According to Einstein’s equation \( K_{\text{max}} = h(\nu - \nu_0) \), increasing the frequency of the incident light while keeping intensity constant raises the energy of each photon. This increase leads to a higher kinetic energy in the emitted photoelectrons but does not affect their number, which is intensity-dependent.
Explanation:
According to Einstein’s equation \( K_{\text{max}} = h(\nu - \nu_0) \), increasing the frequency of the incident light while keeping intensity constant raises the energy of each photon. This increase leads to a higher kinetic energy in the emitted photoelectrons but does not affect their number, which is intensity-dependent.
22. In a photoelectric experiment, if the intensity of light is increased while keeping frequency below the threshold frequency, what would be the outcome?
A. Photoelectrons are emitted with higher kinetic energy.
B. The number of emitted photoelectrons increases.
C. Photoelectrons are emitted at a faster rate.
D. No photoelectric emission occurs.
The correct answer is D. No photoelectric emission occurs.
Explanation:
The threshold frequency is the minimum frequency required to release photoelectrons. If the frequency of light is below this threshold, no photoemission takes place, regardless of the light's intensity.
Explanation:
The threshold frequency is the minimum frequency required to release photoelectrons. If the frequency of light is below this threshold, no photoemission takes place, regardless of the light's intensity.
23. If light with frequency just at the threshold frequency illuminates a metal surface, what is the kinetic energy of the emitted photoelectrons?
A. Equal to the frequency of the light.
B. Equal to Planck’s constant.
C. Zero
D. Proportional to light intensity.
The correct answer is C. Zero.
Explanation:
At threshold frequency \( \nu_0 \), the energy of the photons is just enough to overcome the work function \( \phi_0 \) of the metal, with no extra energy left for kinetic energy. Thus, the kinetic energy of the emitted photoelectrons is zero.
Explanation:
At threshold frequency \( \nu_0 \), the energy of the photons is just enough to overcome the work function \( \phi_0 \) of the metal, with no extra energy left for kinetic energy. Thus, the kinetic energy of the emitted photoelectrons is zero.
24. Which of the following scenarios would increase the number of photoelectrons emitted per second in a photoelectric experiment?
A. Increasing the intensity of incident light while keeping frequency constant and above threshold.
B. Increasing the frequency of light beyond threshold without changing intensity.
C. Decreasing the work function of the metal.
D. Lowering the threshold frequency of the incident light.
The correct answer is A. Increasing the intensity of incident light while keeping frequency constant and above threshold.
Explanation:
The number of photoelectrons emitted per second is proportional to the intensity of the incident light, provided that the frequency is above the threshold. Increasing intensity means more photons striking the surface per second, resulting in more photoelectrons.
Explanation:
The number of photoelectrons emitted per second is proportional to the intensity of the incident light, provided that the frequency is above the threshold. Increasing intensity means more photons striking the surface per second, resulting in more photoelectrons.
25. Which observation in the photoelectric effect experiment contradicts the classical wave theory of light?
A. Emission rate increases with light intensity.
B. Emission occurs after some delay when light is shone.
C. Emission occurs instantly, regardless of light intensity.
D. Kinetic energy depends on light intensity.
The correct answer is C. Emission occurs instantly, regardless of light intensity.
Explanation:
According to classical wave theory, energy is accumulated over time, implying that emission should not be immediate. However, in the photoelectric effect, electrons are emitted instantly as soon as they absorb photons above the threshold frequency, contradicting the classical wave model.
Explanation:
According to classical wave theory, energy is accumulated over time, implying that emission should not be immediate. However, in the photoelectric effect, electrons are emitted instantly as soon as they absorb photons above the threshold frequency, contradicting the classical wave model.
26. According to the photon theory of light, which of the following statements is correct about the energy of photons when the intensity of light of a given wavelength is increased?
A. The energy of each photon increases.
B. The number of photons per second increases, but each photon has the same energy.
C. The momentum of each photon increases.
D. Both the energy and the momentum of each photon increase.
The correct answer is B. The number of photons per second increases, but each photon has the same energy.
Explanation:
The energy of each photon is determined by its frequency \(E = h \\nu\). Increasing the light intensity increases the number of photons per second, not the energy of individual photons.
Explanation:
The energy of each photon is determined by its frequency \(E = h \\nu\). Increasing the light intensity increases the number of photons per second, not the energy of individual photons.
27. What experimental phenomenon provided the first concrete evidence that light behaves as particles (photons) when interacting with matter?
A. Interference of light
B. Diffraction of light
C. Photoelectric effect
D. Reflection of light
The correct answer is C. Photoelectric effect.
Explanation:
The photoelectric effect showed that light behaves as discrete packets of energy, or photons, when interacting with matter. Only light above a certain frequency could eject electrons, a key indicator of particle-like behavior.
Explanation:
The photoelectric effect showed that light behaves as discrete packets of energy, or photons, when interacting with matter. Only light above a certain frequency could eject electrons, a key indicator of particle-like behavior.
28. If a photon has a frequency \\( \\nu \\), which of the following correctly represents its momentum?
A. \( p = h \\nu \)
B. \( p = \\frac{h \\nu}{c} \)
C. \( p = h \\lambda \)
D. \( p = h \\nu \\lambda \)
The correct answer is B. \\( p = \\frac{h \\nu}{c} \\).
Explanation:
The momentum \( p \) of a photon is given by \( p = \\frac{h \\nu}{c} \\), indicating that a photon's momentum is directly proportional to its frequency.
Explanation:
The momentum \( p \) of a photon is given by \( p = \\frac{h \\nu}{c} \\), indicating that a photon's momentum is directly proportional to its frequency.
29. Which experiment confirmed the particle-like behavior of light by demonstrating that photons possess momentum, affecting electron scattering?
A. Young’s double-slit experiment
B. Compton scattering experiment
C. Rutherford scattering experiment
D. Stern-Gerlach experiment
The correct answer is B. Compton scattering experiment.
Explanation:
The Compton scattering experiment by A.H. Compton showed that photons can transfer momentum to electrons, supporting the particle nature of light by demonstrating momentum exchange between photons and electrons.
Explanation:
The Compton scattering experiment by A.H. Compton showed that photons can transfer momentum to electrons, supporting the particle nature of light by demonstrating momentum exchange between photons and electrons.
30. Which of the following best describes the relationship between wavelength and momentum for particles according to de Broglie's hypothesis?
A. \\( \\lambda = \\frac{h}{mv} \\)
B. \\( \\lambda = h \\cdot mv \\)
C. \\( \\lambda = \\frac{mv}{h} \\)
D. \\( \\lambda = \\frac{h}{2mv} \\)
The correct answer is A. \\( \\lambda = \\frac{h}{mv} \\).
Explanation:
De Broglie proposed that particles such as electrons have a wavelength \\( \\lambda = \\frac{h}{mv} \\), relating wave-like properties of particles to momentum.
Explanation:
De Broglie proposed that particles such as electrons have a wavelength \\( \\lambda = \\frac{h}{mv} \\), relating wave-like properties of particles to momentum.
31. Which of the following scenarios would lead to an increase in the number of photons but not the energy per photon?
A. Increasing the intensity of light at a constant frequency
B. Increasing the frequency of light at a constant intensity
C. Decreasing the wavelength at a constant intensity
D. Increasing both frequency and intensity of light
The correct answer is A. Increasing the intensity of light at a constant frequency.
Explanation:
Increasing the intensity of light while maintaining the frequency simply increases the number of photons, each with the same energy \( E = h \\nu \). Changing frequency would alter the energy per photon.
Explanation:
Increasing the intensity of light while maintaining the frequency simply increases the number of photons, each with the same energy \( E = h \\nu \). Changing frequency would alter the energy per photon.
32. During the Compton scattering experiment, which conservation principle was primarily used to validate the photon theory of light?
A. Conservation of electric charge
B. Conservation of momentum and energy
C. Conservation of mass-energy equivalence
D. Conservation of photon number
The correct answer is B. Conservation of momentum and energy.
Explanation:
Compton's experiment verified that momentum and energy were conserved in photon-electron interactions, thereby supporting the particle nature of light. This conservation confirmed the existence of photon momentum.
Explanation:
Compton's experiment verified that momentum and energy were conserved in photon-electron interactions, thereby supporting the particle nature of light. This conservation confirmed the existence of photon momentum.
33. A photon is absorbed in a collision with an electron, transferring all of its energy. Which characteristic of photons makes this interaction unique compared to classical wave interactions?
A. Photons have variable energy based on intensity
B. Photons have quantized energy based on frequency
C. Photons carry an electric charge
D. Photons increase in number upon collision
The correct answer is B. Photons have quantized energy based on frequency.
Explanation:
The energy of a photon is quantized and proportional to its frequency \( E = h \\nu \), allowing it to transfer discrete energy packets in collisions, unlike classical waves where energy can vary continuously with intensity.
Explanation:
The energy of a photon is quantized and proportional to its frequency \( E = h \\nu \), allowing it to transfer discrete energy packets in collisions, unlike classical waves where energy can vary continuously with intensity.
34. Which observation directly supports the idea that particles of matter, like electrons, exhibit wave properties under certain conditions?
A. Photoelectric effect
B. Electron diffraction by a crystal lattice
C. Doppler effect in sound
D. Refraction of light through glass
The correct answer is B. Electron diffraction by a crystal lattice.
Explanation:
Electron diffraction by a crystal lattice confirms the wave nature of particles, as diffraction is a characteristic of waves. This behavior is predicted by de Broglie’s hypothesis, where particles have a wavelength associated with their momentum.
Explanation:
Electron diffraction by a crystal lattice confirms the wave nature of particles, as diffraction is a characteristic of waves. This behavior is predicted by de Broglie’s hypothesis, where particles have a wavelength associated with their momentum.
35. Which property differentiates the energy of a photon from the energy of a macroscopic particle moving at the same speed?
A. Photon energy is affected by mass
B. Photon energy depends solely on its frequency
C. Photon energy increases with speed
D. Photon energy is calculated using kinetic energy formulas
The correct answer is B. Photon energy depends solely on its frequency.
Explanation:
Unlike macroscopic particles, which have kinetic energy dependent on mass and speed, photon energy is independent of speed and mass, depending only on frequency as given by \( E = h \\nu \).
Explanation:
Unlike macroscopic particles, which have kinetic energy dependent on mass and speed, photon energy is independent of speed and mass, depending only on frequency as given by \( E = h \\nu \).
.png)
0 Comments