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JEE Mains · Physics · STD 12 - 11. Dual nature of radiation and matter
Surface of certain metal is first illuminated with light of wavelength \({\lambda _1} = 350\,nm\) and then, the light of wavelength \({\lambda _2} = 540\,nm\). It is found that the maximum speed of the photo electrons in the two cases differ by a factor of \(2\). The work function of the metal (in \(eV\)) is close to: (Energy of photon \( = \frac{{1240}}{{\lambda {\rm{(in\, nm)}}}}\,eV\))
- A \(1.8\)
- B \(2.5\)
- C \(5.6\)
- D \(1.4\)
Answer & Solution
Correct Answer
(A) \(1.8\)
Step-by-step Solution
Detailed explanation
\(\frac{1240}{350}-\phi=(\mathrm{KE})_{1}=4 \mathrm{x}\) ..... \((1)\) \(\frac{1240}{540}-\phi=(\mathrm{KE})_{11}=x\) ...... \((2)\) \((1)\,\,-\,\,(2)\) \(\frac{1240}{350}-\frac{1240}{540}=3.542-2.296=3 x\) \(1.246=3 x ; \quad x=0.41\) \(\phi=2.296-0.41=1.886\)
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