Chapter 11: Dual Nature of Radiation and Matter Assertion-Reason Questions | physics Class 12 CBSE

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 1

Logic Check

Assertion (A): The photoelectric current increases when the intensity of incident light is increased, keeping frequency constant. Reason (R): Higher intensity means more photons per second, so more photoelectrons are emitted per second.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 2

Logic Check

Assertion (A): The stopping potential is independent of the intensity of incident radiation. Reason (R): Stopping potential depends on the maximum kinetic energy of photoelectrons, which is determined by the frequency of incident radiation, not its intensity.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 3

Logic Check

Assertion (A): No photoelectric emission occurs from zinc when red light is incident on it. Reason (R): Red light has a frequency lower than the threshold frequency of zinc, so each photon does not have enough energy to overcome the work function of zinc.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 4

Logic Check

Assertion (A): Photoelectric emission is an instantaneous process with no apparent time lag. Reason (R): In Einstein's photon model, the absorption of a single photon by a single electron is an elementary event requiring no energy accumulation time.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 5

Logic Check

Assertion (A): The de Broglie wavelength of a cricket ball is not observable. Reason (R): The de Broglie wavelength of macroscopic objects is so small (of the order of 10⁻³⁴ m) that it is far beyond the resolution of any measuring instrument.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 6

Logic Check

Assertion (A): The slope of the V₀ versus frequency graph is the same for all photosensitive materials. Reason (R): The slope equals h/e, where both h (Planck's constant) and e (elementary charge) are universal constants independent of the material.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 7

Logic Check

Assertion (A): In the photoelectric effect, maximum kinetic energy of photoelectrons increases linearly with the frequency of incident radiation. Reason (R): According to Einstein's equation Kmax = hν − φ₀, for a given metal (constant φ₀), Kmax varies linearly with ν.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 8

Logic Check

Assertion (A): Photons are not deflected by electric or magnetic fields. Reason (R): Photons carry electric charge equal to the elementary charge e.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 9

Logic Check

Assertion (A): Alkali metals like caesium and potassium are used in photoelectric cells that operate under visible light. Reason (R): Alkali metals have lower work functions, so their threshold frequencies fall within the visible light range.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 10

Logic Check

Assertion (A): The de Broglie wavelength of an electron is comparable to X-ray wavelengths. Reason (R): The electron has a very small mass, so even at moderate speeds its momentum is small enough to give a wavelength in the sub-nanometre range.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 11

Logic Check

Assertion (A): Increasing the intensity of incident radiation below the threshold frequency will eventually cause photoelectric emission. Reason (R): Higher intensity delivers more energy to the metal surface, eventually enabling electrons to overcome the work function.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 12

Logic Check

Assertion (A): In a photon-electron collision, the total energy and total momentum are conserved. Reason (R): The number of photons is also conserved in every photon-electron collision.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 13

Logic Check

Assertion (A): The wave theory of light cannot explain the existence of a threshold frequency in the photoelectric effect. Reason (R): According to wave theory, the energy delivered to electrons depends on intensity, so any frequency of light should cause emission given sufficient intensity.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 14

Logic Check

Assertion (A): Millikan's experiments between 1906–1916 confirmed Einstein's photoelectric equation. Reason (R): Millikan designed these experiments specifically to prove Einstein's equation correct.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 15

Logic Check

Assertion (A): The de Broglie wavelength decreases when the momentum of the particle increases. Reason (R): According to the de Broglie relation λ = h/p, wavelength is inversely proportional to momentum.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 16

Logic Check

Assertion (A): The saturation current is the same for two different frequencies of incident radiation at the same intensity. Reason (R): Saturation current depends on the number of photoelectrons emitted per second, which is proportional to intensity, not frequency.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 17

Logic Check

Assertion (A): The work function of a metal is the maximum energy required by an electron to escape from its surface. Reason (R): Work function is the least energy required by an electron to come out of the metal surface.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 18

Logic Check

Assertion (A): All photoelectrons emitted from a metal surface have the same kinetic energy. Reason (R): Each photoelectron absorbs one photon of the same energy hν, so all have the same kinetic energy hν − φ₀.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 19

Logic Check

Assertion (A): De Broglie's hypothesis predicts that matter waves are associated only with charged particles like electrons and protons. Reason (R): The de Broglie relation λ = h/p is universal and applies to all moving particles regardless of charge or nature.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 20

Logic Check

Assertion (A): The phenomenon of interference of light establishes its wave nature. Reason (R): The photoelectric effect establishes the particle nature of light.

Reasoning Options

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Chapter sections

Chapter 11: Dual Nature of Radiation and Matter | Assertion-Reason

Assertion (A): The photoelectric current increases when the intensity of incident light is increased, keeping frequency constant. Reason (R): Higher intensity means more photons per second, so more photoelectrons are emitted per second.

Assertion (A): The stopping potential is independent of the intensity of incident radiation. Reason (R): Stopping potential depends on the maximum kinetic energy of photoelectrons, which is determined by the frequency of incident radiation, not its intensity.

Assertion (A): No photoelectric emission occurs from zinc when red light is incident on it. Reason (R): Red light has a frequency lower than the threshold frequency of zinc, so each photon does not have enough energy to overcome the work function of zinc.

Assertion (A): Photoelectric emission is an instantaneous process with no apparent time lag. Reason (R): In Einstein's photon model, the absorption of a single photon by a single electron is an elementary event requiring no energy accumulation time.

Assertion (A): The de Broglie wavelength of a cricket ball is not observable. Reason (R): The de Broglie wavelength of macroscopic objects is so small (of the order of 10⁻³⁴ m) that it is far beyond the resolution of any measuring instrument.

Assertion (A): The slope of the V₀ versus frequency graph is the same for all photosensitive materials. Reason (R): The slope equals h/e, where both h (Planck's constant) and e (elementary charge) are universal constants independent of the material.

Assertion (A): In the photoelectric effect, maximum kinetic energy of photoelectrons increases linearly with the frequency of incident radiation. Reason (R): According to Einstein's equation Kmax = hν − φ₀, for a given metal (constant φ₀), Kmax varies linearly with ν.

Assertion (A): Photons are not deflected by electric or magnetic fields. Reason (R): Photons carry electric charge equal to the elementary charge e.

Assertion (A): Alkali metals like caesium and potassium are used in photoelectric cells that operate under visible light. Reason (R): Alkali metals have lower work functions, so their threshold frequencies fall within the visible light range.

Assertion (A): The de Broglie wavelength of an electron is comparable to X-ray wavelengths. Reason (R): The electron has a very small mass, so even at moderate speeds its momentum is small enough to give a wavelength in the sub-nanometre range.

Assertion (A): Increasing the intensity of incident radiation below the threshold frequency will eventually cause photoelectric emission. Reason (R): Higher intensity delivers more energy to the metal surface, eventually enabling electrons to overcome the work function.

Assertion (A): In a photon-electron collision, the total energy and total momentum are conserved. Reason (R): The number of photons is also conserved in every photon-electron collision.

Assertion (A): The wave theory of light cannot explain the existence of a threshold frequency in the photoelectric effect. Reason (R): According to wave theory, the energy delivered to electrons depends on intensity, so any frequency of light should cause emission given sufficient intensity.

Assertion (A): Millikan's experiments between 1906–1916 confirmed Einstein's photoelectric equation. Reason (R): Millikan designed these experiments specifically to prove Einstein's equation correct.

Assertion (A): The de Broglie wavelength decreases when the momentum of the particle increases. Reason (R): According to the de Broglie relation λ = h/p, wavelength is inversely proportional to momentum.

Assertion (A): The saturation current is the same for two different frequencies of incident radiation at the same intensity. Reason (R): Saturation current depends on the number of photoelectrons emitted per second, which is proportional to intensity, not frequency.

Assertion (A): The work function of a metal is the maximum energy required by an electron to escape from its surface. Reason (R): Work function is the least energy required by an electron to come out of the metal surface.

Assertion (A): All photoelectrons emitted from a metal surface have the same kinetic energy. Reason (R): Each photoelectron absorbs one photon of the same energy hν, so all have the same kinetic energy hν − φ₀.

Assertion (A): De Broglie's hypothesis predicts that matter waves are associated only with charged particles like electrons and protons. Reason (R): The de Broglie relation λ = h/p is universal and applies to all moving particles regardless of charge or nature.

Assertion (A): The phenomenon of interference of light establishes its wave nature. Reason (R): The photoelectric effect establishes the particle nature of light.

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