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JEE Advanced Chemistry Structure of Atom 2021 JEE Advanced 2021 (Paper 2)

JEE Advanced Chemistry Question (2021) — Solution

Question

Consider a helium He atom that absorbs a photon of wavelength 330   nm . The change in the velocity (in cm   s - 1 ) of He atom after the photon absorption is ______ . (Assume: Momentum is conserved when photon is absorbed. Use: Planck constant = 6 . 6 × 10 - 34   J   s , Avocados number = 6 × 10 23   mol - 1 , Molar mass of He = 4   g   mol - 1 )

Options

  1. A. A
  2. B. B
  3. C. C
  4. D. D

Answer

A. A

Step-by-step solution

P = h λ mv = h λ v = h mλ v = 6 .6 × 10 − 34 × 6 × 10 23 4 × 10 − 3 × 330 × 10 − 9 v = 3 × 10 − 1   m / s v = 30   cm / s ∆ v   =   v f - v i = v - 0 = v   =   30   cm / s

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