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JEE Main 2021 (27 Aug, Shift 2) · Photoelectric Effect: Einstein's Equation

Photoelectric Effect: Einstein's Equation question from JEE Main 2021 (27 Aug, Shift 2)

Q108JEE Main 2021 · 27 AUG · SHIFT 2Medium

Photoelectric Effect: Einstein's Equation

A monochromatic neon lamp with wavelength of 670.5 nm illuminates a photo-sensitive material which has a stopping voltage of 0.48 V. What will be the stopping voltage if the source light is changed with another source of wavelength of 474.6 nm?

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Answer: (b)

  1. Use E(eV)=1240λ(nm)E(\text{eV}) = \frac{1240}{\lambda(\text{nm})}
  2. E1=1240670.5=1.849 eV⇒ϕ=1.849−0.48=1.369 eVE_1 = \frac{1240}{670.5} = 1.849\text{ eV} \Rightarrow \phi = 1.849 - 0.48 = 1.369\text{ eV}
  3. E2=1240474.6=2.613 eVE_2 = \frac{1240}{474.6} = 2.613\text{ eV}
  4. V2=2.613−1.369=1.24 VV_2 = 2.613 - 1.369 = 1.24\text{ V}
  5. So the answer is (b) 1.25 V.
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