JEE Main · 2023 · 31 Jan 2023 · Shift 2 · Modern Physics

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If the two metals A and B are exposed to radiation of wavelength 350 nm. The work functions of metals A and B are 4.8 eV and 2.2 eV. Then choose the correct option

(A)Metal B will not emit photo-electrons
(B)Both metals A and B will emit photo-electrons
(C)Both metals A and B will not emit photoelectrons
(D)Metal A will not emit photo-electrons✓ Correct

Answer: (D)

Solution

Each photon of the

350 nm

light carries an energy

E = \frac{h c}{λ} = \frac{1240 eV nm}{350 nm} \approx 3.54 eV

. Emission happens only when this exceeds the work function. For metal B, whose work function is

2.2 eV

, the photon has energy to spare and electrons are ejected; for metal A, needing

4.8 eV

, the photon falls short. Electrons are released from metal B, while metal A emits none.

JEE Main · 2023 · 31 Jan 2023 · Shift 2 · Single correct option

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