Q. 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) Diffraction pattern is not observed on the screen in the case of electrons
B) The angular width of the central maximum of the diffraction pattern will increase
C) The angular width of the central maximum will decrease
D) The angular width of the central maximum will be unaffected
Explanation
[Solution from source] Faster electrons have a smaller de Broglie wavelength λ = h/(mv). The angular width of the central maximum is about 2λ/a, so it decreases. Electrons do show diffraction because of their wave nature. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.