JEE Main 2020 — Physics Modern Physics

2020mcqhard

Particle $A$ of mass ${\text{m}}_{\text{A}}=\frac{\text{m}}{2}$ moving along the $\text{x}$ -axis with velocity ${\text{v}}_{0}$ collides elastically with another particle $\text{B}$ at rest having mass ${\text{m}}_{\text{B}}=\frac{\text{m}}{3}$ . If both the particles move along the $\text{x}$ -axis after the collision, the change $\Delta \lambda$ in the wavelength of the particle $\text{A}$ , in terms of its de-Broglie wavelength $({\lambda }_{0})$ before the collision is:

Official previous-year question

Held on 4 Sept 2020 · Verified 6 Jul 2026.

Options

A
$\Delta \lambda =\frac{3}{2}{\lambda }_{0}$
B
$\Delta \lambda =\frac{5}{2}{\lambda }_{0}$
C
$\Delta \lambda =2{\lambda }_{0}$
D
$\Delta \lambda =4{\lambda }_{0}$

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Solution

JEE Main 2020 Physics, Dual Nature of Matter — solution figure

${v}_{1}=\frac{2(m/3)0}{(\frac{m}{2}+\frac{m}{3})}+\frac{(\frac{m}{2}-\frac{m}{3})v}{(\frac{m}{2}+\frac{m}{3})}=\frac{v}{5}$

For particle $A$ ,

Initial de-Broglie wavelength

${\lambda }_{0}=\frac{h}{\frac{m}{2}v}=\frac{2h}{\mathrm{mv}}$

Final de-Broglie wavelength after collision.

${\lambda }_{1}=\frac{h}{\frac{m}{2}\frac{v}{5}}=\frac{10h}{\mathrm{mv}}=5{\lambda }_{0}$

Change in De-Broglie wavelength $\Delta \lambda ={\lambda }_{i}-{\lambda }_{0}=4{\lambda }_{0}$

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Solution

JEE Main 2020 Physics, Dual Nature of Matter — solution figure

${v}_{1}=\frac{2(m/3)0}{(\frac{m}{2}+\frac{m}{3})}+\frac{(\frac{m}{2}-\frac{m}{3})v}{(\frac{m}{2}+\frac{m}{3})}=\frac{v}{5}$

For particle $A$ ,

Initial de-Broglie wavelength

${\lambda }_{0}=\frac{h}{\frac{m}{2}v}=\frac{2h}{\mathrm{mv}}$

Final de-Broglie wavelength after collision.

${\lambda }_{1}=\frac{h}{\frac{m}{2}\frac{v}{5}}=\frac{10h}{\mathrm{mv}}=5{\lambda }_{0}$

Change in De-Broglie wavelength $\Delta \lambda ={\lambda }_{i}-{\lambda }_{0}=4{\lambda }_{0}$

JEE Main 2020 — Physics Modern Physics

Options

Did you get this right?

Solution

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JEE Main Modern Physics in other years

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JEE Main 2020 — Physics Modern Physics

Options

Did you get this right?

Solution

Your note

JEE Main Modern Physics in other years

More JEE Main Modern Physics questions

Other Physics topics for JEE Main

Mechanics

Electromagnetism

Optics

Thermodynamics

Waves & Oscillations

Keep practicing Modern Physics