A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from slit. If speed of electrons is increased, which statement is correct?
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Question

A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from slit. If speed of electrons is increased, which statement is correct?

Options

G1 Physics · Accepted Answer

Step 1: Electrons show de Broglie diffraction with wavelength λ = h/p. Step 2: At non-relativistic speed p = mv, so increasing v decreases λ. Step 3: Angular width of central maximum θ ≈ 2λ/a decreases with λ. Final answer: (C) decrease.