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JEE Main 2015 (10 Apr, Shift 1) · Davisson-Germer, Uncertainty, Compton & X-Rays

Davisson-Germer, Uncertainty, Compton & X-Rays question from JEE Main 2015 (10 Apr, Shift 1)

Q15JEE Main 2015 · 10 APR · SHIFT 1Medium

Davisson-Germer, Uncertainty, Compton & X-Rays

A parallel beam of electrons travelling in x-direction falls on a slit of width d (see figure). If after passing the slit, an electron acquires momentum py in the y-direction then for a majority of electrons passing through the slit (h is Planck's constant):

Figure

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Answer: (c)

  1. Most electrons land inside the central maximum, where sin⁡θ<λd\sin\theta < \frac{\lambda}{d}.
  2. py=psin⁡θ<pλdp_y = p\sin\theta < p\frac{\lambda}{d}, and pλ=hp\lambda = h.
  3. ∣py∣<hd⇒∣py∣d<h|p_y| < \frac{h}{d} \Rightarrow |p_y|d < h
  4. So the answer is (c).
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