Dual Nature of Matter

JEE Main level, single correct, medium

196 of 200

Question 196 of 200

The work function of a substance is 4.0eV4.0 \mathrm{eV}. Then longest wavelength of light that can cause photoelectron emission from this substance approximately

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Answer: (C) 310 nm310 \mathrm{~nm}

hcλ=W\frac{\mathrm{hc}}{\lambda}=\mathrm{W}
λlongest =hcW=6.6×10−34×3×1084.0×1.6×10−19\lambda_{\text {longest }}=\frac{\mathrm{hc}}{\mathrm{W}}=\frac{6.6 \times 10^{-34} \times 3 \times 10^8}{4.0 \times 1.6 \times 10^{-19}}
⇒λlongest ≈310 nm\Rightarrow \lambda_{\text {longest }} \approx 310 \mathrm{~nm}.

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