NEET Physics: Photoelectric effect Practice Questions

Correct answer: D — Intensity determines the number of photons striking the surface, which affects the number of emitted electrons.

The intensity of light affects the number of photons incident on the surface. However, once the threshold frequency is exceeded, the energy of each individual photon dictates the maximum kinetic energy (Kₘₐₓ), not the intensity.

Correct answer: C — Zero

When the frequency of incident light is exactly equal to the threshold frequency (f₀), the minimum energy required for photoemission is supplied. In this specific case, the work function is entirely used to release the maximum kinetic energy of the emitted photoelectrons, resulting in a kinetic energy equal to the energy of the incident photon, Eₚₕₒₜₒₙ = hf₀, which equals hν (where ν is the threshold frequency).

Correct answer: B — It relates the energy of a photon to its frequency.

Planck's constant (h) is the proportionality constant that links the energy (E) of a photon to its frequency (f), making it central to the energy quantization in the photoelectric effect.

Correct answer: C — work function

The minimum energy required to free an electron from a metal surface is defined as the work function (φ). This energy is necessary regardless of the frequency of the incident light (if φ is not supplied, no emission occurs).

Correct answer: A — Threshold frequency

The threshold frequency (f₀) is the minimum frequency of incident light required to cause photoemission. Below this frequency, no photoemission occurs, regardless of the intensity of the light.

Correct answer: A — Planck's constant

The relationship between the energy of a quantum of light (E) and its frequency (f) is given by E = hf, where h is Planck's constant.

Correct answer: B — E = hf

The photoelectric effect is explained by the equation E = hf, where E is the energy of the photon, h is Planck's constant, and f is the frequency of the incident light.

Correct answer: C — hν- φ

According to Einstein's photoelectric equation, E = hν= φ+ Kₘₐₓ, where Kₘₐₓ is the maximum kinetic energy of the emitted photoelectrons. If hν= φ, then Kₘₐₓ = 0. This means the emitted photoelectrons have zero kinetic energy (they just reach the threshold velocity).

Correct answer: D — No photoemission occurs

If the incident photon energy (hf) is less than the work function (φ), no photoemission occurs because the energy is insufficient.

Correct answer: C — Threshold frequency

The minimum energy required to eject an electron is related to the work function (φ). The minimum frequency required is the threshold frequency (f₀), which corresponds to the threshold energy (φ= hf₀).

Correct answer: C — The frequency of the incident radiation.

The maximum kinetic energy (KEₘₐₓ) of the emitted photoelectron is given by KEₘₐₓ = hf - φ. Therefore, it is directly dependent on the frequency (f) of the incident radiation, provided hf > φ.

Correct answer: C — Threshold frequency

The threshold frequency (f₀) is the minimum frequency required to eject an electron. This threshold is dependent on the material's work function (φ).