NEET Physics Question - Modern Physics - Photoelectric Effects and deBroglie Equation

Assertion (A): When ultraviolet light incident on a photo cell, its stopping potential is \(V_S\) and the maximum kinetic energy of photoelectrons is \(K_{\text{max}}\) . When the ultraviolet light is replaced by X-rays, both \(V_S\) and \(K_{\text{max}}\) increases.

Reason (R): Photo electrons are emitted with speed ranging from zero to a maximum value because of the range of frequencies present in the incident light.

Both (A) & (R) are true and the (R) is the correct explanation of the (A)

Both (A) & (R) are true but the (R) is not the correct explanation of the (A)

(A) is true but (R) is false

Both (A) and (R) are false

Solution:

Concept: Photoelectric effect and photon energy.
Formula: \(K_{\text{max}} = hf - \phi\) and \(eV_s = K_{\text{max}}\) where \(f\) is frequency.
Solution: X-rays have higher frequency and thus higher photon energy than ultraviolet light. Therefore, incident X-rays will produce photoelectrons with higher maximum kinetic energy (\(K_{\text{max}}\) ) and higher stopping potential (\(V_s\) ). So (A) is true. The range of photoelectron speeds is primarily due to energy losses as electrons travel through the material, not necessarily due to a range of frequencies in the incident light. So (R) is false.

Rankers Physics

Photoelectric Effect: UV vs. X-rays

Solution:

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