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Dual Nature of Radiation question

2025 · 29 Jan · Shift 2 · Q52
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Dual Nature of Radiation question

2025 · 29 Jan · Shift 2 · Q52

JEE MainPhysicsDual Nature of RadiationMCQ+4 / −1
In an experiment with photoelectric effect, the stopping potential,
  1. A
    is (1e)\left(\frac{1}{e}\right)(e1​) times the maximum kinetic energy of the emitted photoelectrons
  2. B
    increases with increase in the intensity of the incident light
  3. C
    decreases with increase in the intensity of the incident light
  4. D
    increases with increase in the wavelength of the incident light
View written solutionFree

Correct answer: A

  1. Relation between stopping potential and maximum kinetic energy

In the photoelectric effect, the maximum kinetic energy of emitted photoelectrons is related to stopping potential V0V_0V0​ by

Kmax⁡=eV0K_{\max} = eV_0Kmax​=eV0​

where eee is the electronic charge.

So,

V0=Kmax⁡eV_0 = \frac{K_{\max}}{e}V0​=eKmax​​

This means the stopping potential is indeed (1e)\left(\frac{1}{e}\right)(e1​) times the maximum kinetic energy.

So Option A is correct.


  1. Dependence on intensity of incident light

From Einstein’s photoelectric equation,

Kmax⁡=hν−ϕK_{\max} = h\nu - \phiKmax​=hν−ϕ

where:

  • hνh\nuhν is the photon energy,
  • ϕ\phiϕ is the work function.

Thus Kmax⁡K_{\max}Kmax​, and hence stopping potential V0V_0V0​, depends on the frequency of incident light, not on its intensity.

So:

  • Option B: "increases with increase in intensity" →\to→ False
  • Option C: "decreases with increase in intensity" →\to→ False

Intensity affects the number of emitted electrons (photoelectric current), not their maximum kinetic energy.


  1. Dependence on wavelength

Since

ν=cλ\nu = \frac{c}{\lambda}ν=λc​

increasing wavelength λ\lambdaλ decreases frequency ν\nuν, so photon energy hνh\nuhν decreases.

Therefore,

Kmax⁡=hν−ϕK_{\max} = h\nu - \phiKmax​=hν−ϕ

also decreases with increase in wavelength (provided emission still occurs). Hence stopping potential decreases, not increases.

So Option D is false.


  1. Final evaluation of options
  • A: True
  • B: False
  • C: False
  • D: False

Therefore, the single correct answer is A.

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