JEE Main · 2026 · 21 Jan 2026 · Shift 1 · Modern Physics

A light wave described by

E = 60 sin (3 \times 1 0^{15}) t + sin (12 \times 1 0^{15})

t] (in SI units) falls on a metal surface of work function 2.8 eV . The maximum kinetic energy of ejected photoelectron is (approximately)
____ eV.

(h = 6.6 \times 1 0^{- 34} J - s .

and

e = 1.6 \times 1 0^{- 19} C

)

(A)5.1✓ Correct
(B)3.8
(C)6.0
(D)7.8

Answer: (A)

Solution

The beam contains two angular frequencies,

ω_{1} = 3 \times 1 0^{15}

and

ω_{2} = 12 \times 1 0^{15} rad/s

; the larger one produces the most energetic photons. Its energy is

E = ℏ ω_{2} = \frac{6.6 \times 1 0 ^{- 34}}{2 π} \times 12 \times 1 0^{15} = 1.26 \times 1 0^{- 18} J \approx 7.9 eV

. The maximum kinetic energy of the ejected electron is

E - ϕ = 7.9 - 2.8 \approx 5.1 eV

JEE Main · 2026 · 21 Jan 2026 · Shift 1 · Single correct option

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