A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. If the speed of the electrons is increased, which of the following statements is correct?A. The angular width of central maximum will be unaffected.B. Diffraction pattern is not observed on the screen in the case of electrons.C. Th angular width of the central maximum of the diffraction pattern will increase.D. The angular width of the central maximum will decrease.

A parallel beam of fast moving electrons is incident normally on a nar

1.	A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. If the speed of the electrons is increased, which of the following statements is correct?A. The angular width of central maximum will be unaffected.B. Diffraction pattern is not observed on the screen in the case of electrons.C. Th angular width of the central maximum of the diffraction pattern will increase.D. The angular width of the central maximum will decrease.
Answer» Correct Answer - D The diffraction pattern of electron beam will be observed on the screen. If the speed of electrons is increased, de Broglie wavelength associated with electron beam decreases `(lambda = h//mv)`. As angular width of central maximum is proportional to `lambda`, therefore, angular width of central maximum will decreses. Choice (d) is correct.

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