Easy MCQ +4 / -1 PYQ · JEE Mains 2025

The work function of a metal is 3 eV . The color of the visible light that is required to cause emission of photoelectrons is

  1. A Red
  2. B Green
  3. C Blue Correct answer
  4. D Yellow

Solution

<p>To determine which color of visible light will cause the emission of photoelectrons from a metal with a work function of 3 eV, we need to consider the relationship between the photon energy, the work function, and the wavelength of light.</p> <p>The maximum kinetic energy ($ \text{KE}_{\max} $) of the emitted photoelectrons is given by:</p> <p>$ \text{KE}_{\max} = \frac{hc}{\lambda} - \phi $</p> <p>For photoemission to occur, the energy of the incident photons must be greater than the work function ($\phi$):</p> <p>$ \frac{hc}{\lambda} > \phi $</p> <p>This implies:</p> <p>$ \lambda < \frac{hc}{\phi} $</p> <p>Substitute the values $ h = 4.135667696 \times 10^{-15} \, \text{eV}\cdot\text{s} $, $ c = 3 \times 10^{8} \, \text{m/s} $, and $\phi = 3 \, \text{eV}$:</p> <p>$ \lambda < \frac{1242}{3} \, \text{nm} \approx 414 \, \text{nm} $</p> <p>Since the wavelength must be less than 414 nm to cause emission, we need light with a shorter wavelength. Among the visible colors, blue light has a wavelength in this range, making it the correct choice. Thus, blue light will cause the emission of photoelectrons with this work function.</p>

About this question

Subject: Physics · Chapter: Dual Nature of Matter and Radiation · Topic: Photoelectric Effect

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