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JEE Main 2020 (4 Sep, Shift 1) · Matter Waves: de Broglie Wavelength

Matter Waves: de Broglie Wavelength question from JEE Main 2020 (4 Sep, Shift 1)

Q119JEE Main 2020 · 4 SEP · SHIFT 1Difficult

Matter Waves: de Broglie Wavelength

Particle A of mass mA = m2\frac{m}{2} moving along the x-axis with velocity v0 collides elastically with another particle B at rest having mass mB = m3\frac{m}{3}. If both particles move along the x-axis after the collision, the change Δλ\Delta\lambda in de-Broglie wavlength of particle A, in terms of its de-Broglie wavelength (λ\lambda0) before collision is:

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Answer: (d)

  1. Elastic, B at rest: vA′=mA−mBmA+mBv0=m/2−m/3m/2+m/3v0=v05v_A' = \dfrac{m_A - m_B}{m_A + m_B}v_0 = \dfrac{m/2 - m/3}{m/2 + m/3}v_0 = \dfrac{v_0}{5}
  2. λA′=hmAv0/5=5λ0\lambda_A' = \dfrac{h}{m_A v_0/5} = 5\lambda_0
  3. Δλ=5λ0−λ0=4λ0\Delta\lambda = 5\lambda_0 - \lambda_0 = 4\lambda_0
  4. So the answer is (d).
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