Modern Physics | JEE Main 2025 Solution

JEE MAIN 2025

23-01-2025 SHIFT-2

Question

In photoelectric effect an em-wave is incident on a metal surface and electrons are ejected from the surface. If the work function of the metal is 2.14 eV and stopping potential is 2 V, what is the wavelength of the em-wave ? (Given hc = 1242 eVnm where h is the Planck's constant and c is the speed of light in vaccum.)

Select the correct option:

200 nm

600 nm

400 nm

300 nm

✓ Correct! Well done.

✗ Incorrect. Try again or view the solution.

Solution

$\mathrm{eV}_{\mathrm{s}}=\mathrm{E}-\phi$
$2 \mathrm{eV}=\mathrm{E}-2.14 \mathrm{eV}$
$\mathrm{E}=4.14 \mathrm{eV}$
$\mathrm{E}=\frac{\mathrm{hc}}{\lambda}$
$\lambda=\frac{1242}{4.14}=300 \mathrm{~nm}$

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