Dual Nature of Matter

JEE Main level, single correct, medium

127 of 200

Question 127 of 200

The difference between threshold wavelengths for two metal surfaces AA and BB having work function ϕA=9eV{\phi }_{A}=9eV and ϕB=4.5eV{\phi }_{B}=4.5eV in nmnm is:
{Given, hc=1242eVnmhc=1242eVnm}

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Answer: (D) 138138

The work function is given by
hcλ=ϕ\dfrac{hc}{\lambda }=\phi
⇒λ=hcϕ\Rightarrow \lambda =\dfrac{hc}{\phi }
By the given data,
λA=12429nm{\lambda }_{A}=\dfrac{1242}{9}nm, λB=12424.5nm{\lambda }_{B}=\dfrac{1242}{4.5}nm,
The difference between the wavelengths,
λB−λA=12424.5−12429nm=12429nm{\lambda }_{B}-{\lambda }_{A}=\dfrac{1242}{4.5}-\dfrac{1242}{9}nm=\dfrac{1242}{9}nm
=138nm=138nm

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