JEE Main · 2025 · 03 Apr 2025 · Shift 1 · Modern Physics

WhatsApp Email

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

(A)Green
(B)Blue✓ Correct
(C)Red
(D)Yellow

Answer: (B)

Solution

Photoelectrons are emitted only when the photon energy reaches the work function,

\frac{h c}{λ} \geq ϕ

, i.e. for wavelengths shorter than the threshold

λ_{0} = \frac{h c}{ϕ} = \frac{1240 eV\cdotnm}{3 eV} \approx 413 nm .

A shorter wavelength carries higher photon energy, so among the visible colours the one able to eject electrons is the one of shortest wavelength. Of the choices offered, blue light has the shortest wavelength and the highest photon energy, so blue light is required to cause photoemission.

JEE Main · 2025 · 03 Apr 2025 · Shift 1 · Single correct option

Practise more: all JEE Main PYQs on Modern Physics →

More JEE Main questions on Modern Physics

7.9 MeV α-particle scatters from a target material of atomic number 79. From the given data the estimated diameter of nuclei of the target material is (approximately) ______ m.
[ $\frac{1}{4 π ϵ _{0}} = 9 \times 1 0^{9}$ Nm²/C² and electron charge $= 1.6 \times 1 0^{- 19}$ C]
JEE Main 2026View solution →
The minimum frequency of photon required to break a particle of mass 15.348 amu into $4 α$ particles is ______ kHz.
[mass of He nucleus = 4.002 amu, $1$ amu $= 1.66 \times 1 0^{- 27}$ kg, $h = 6.6 \times 1 0^{- 34}$ J.s and $c = 3 \times 1 0^{8}$ m/s]
JEE Main 2026View solution →
The smallest wavelength of Lyman series is 91 nm. The difference between the largest wavelengths of Paschen and Balmer series is nearly $____$ nm.
JEE Main 2026View solution →
Light is incident on a metallic plate having work function $110 \times 1 0^{- 20} J$ . If the produced photoelectrons have zero kinetic energy then the angular frequency of the incident light is ______ $rad / s$ . ( …
JEE Main 2026View solution →
The energy of an electron in an orbit of the Bohr's atom is $- 0.04 E_{0} eV$ where $E_{0}$ is the ground state energy. If L is the angular momentum of the electron in this orbit and h is the Planck's constant, then …
JEE Main 2026View solution →
A particle having electric charge $3 \times 1 0^{- 19} C$ and mass $6 \times 1 0^{- 27} kg$ is accelerated by applying an electric potential of 1.21 V . Wavelength of the matter wave associated with the particle is $α \times 1 0^{- 12} m$ . The va …
JEE Main 2026View solution →