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Dual Nature of Radiation question

2025 · 29 Jan · Shift 1 · Q51
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  5. /2025 · 29 Jan · Shift 1 · Q51

Dual Nature of Radiation question

2025 · 29 Jan · Shift 1 · Q51

JEE MainPhysicsDual Nature of RadiationMCQ+4 / −1
If λ\lambdaλ and KKK are de Broglie wavelength and kinetic energy, respectively, of a particle with constant mass. The correct graphical representation for the particle will be :
  1. A
    JEE Main 2025 (Online) 29th January Morning Shift Physics - Dual Nature of Radiation Question 20 English Option 1
  2. B
    JEE Main 2025 (Online) 29th January Morning Shift Physics - Dual Nature of Radiation Question 20 English Option 2
  3. C
    JEE Main 2025 (Online) 29th January Morning Shift Physics - Dual Nature of Radiation Question 20 English Option 3
  4. D
    JEE Main 2025 (Online) 29th January Morning Shift Physics - Dual Nature of Radiation Question 20 English Option 4
View written solutionFree

Correct answer: D

  1. For a particle of constant mass mmm, the de Broglie wavelength is
λ=hp\lambda = \frac{h}{p}λ=ph​

where ppp is momentum.

  1. For a non-relativistic particle, kinetic energy is
K=p22mK = \frac{p^2}{2m}K=2mp2​

So,

p=2mKp = \sqrt{2mK}p=2mK​
  1. Substitute this into the de Broglie relation:
λ=h2mK\lambda = \frac{h}{\sqrt{2mK}}λ=2mK​h​

Thus,

λ∝1K\lambda \propto \frac{1}{\sqrt{K}}λ∝K​1​
  1. Rearranging,
λ2=h22mK\lambda^2 = \frac{h^2}{2mK}λ2=2mKh2​

which gives

K∝1λ2K \propto \frac{1}{\lambda^2}K∝λ21​
  1. Therefore, the graph between λ\lambdaλ and KKK is an inverse-square type curve:
  • as KKK increases, λ\lambdaλ decreases,
  • the curve is not linear,
  • it falls rapidly at first and then more slowly.
  1. Hence, the correct graphical representation must be the one showing
λ∝1K\lambda \propto \frac{1}{\sqrt{K}}λ∝K​1​

or equivalently

K∝1λ2K \propto \frac{1}{\lambda^2}K∝λ21​

which corresponds to Option D.

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