IGNOU BPHET 141 2026 - Electrons are accelerated through and incident on a crystal

Question

Electrons are accelerated through $150\text{V}$ and incident on a crystal with interatomic spacing $d = 0.25\text{ nm}$ . Calculate the de Broglie wavelength and the first-order Bragg diffraction angle.

19 Jan 2026

Answer :

Word Count : 204

The de Broglie wavelength of an electron is given by [ \lambda = \frac{h}{p} = \frac{h}{\sqrt{2 m_e e V}} ] where (h = 6.626 \times 10^{-34} \text{ Js}), (m_e = 9.11 \times 10^{-31} \text{ kg}), (e = 1.602 \times 10^{-19} \text{ C}), and (V = 150 \text{ V}). First, calculate the momentum term under the square root: [ 2 m_e e V =

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