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 the central maximum will decrease. (b) The angular wifth of the central maximum will be unaffected. (c) Diffraction pattern is not observed on the screen in the case of electrons. (d) The angular width of the central maximum of the diffraction pattern will increase.

Answer: (a). Angular width of central maximum = (2λ)/(a), where a is slit width. λ = h/mv, so higher speed gives smaller λ. Smaller λ gives a narrower central maximum. So the answer is (a): the angular width decreases.

A parallel beam of fast moving electrons is incident normally on a… | NEET 2013

Q18NEET 2013Medium

Davisson-Germer, Uncertainty, Compton & X-Rays

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?

Show answer and solution

Answer: (a)

Angular width of central maximum $= \frac{2\lambda}{a}$ , where $a$ is slit width.
$\lambda = \frac{h}{mv}$ , so higher speed gives smaller $\lambda$ .
Smaller $\lambda$ gives a narrower central maximum.
So the answer is (a): the angular width decreases.

Report a mistake

Davisson-Germer, Uncertainty, Compton & X-Rays question from NEET 2013

More questions on Davisson-Germer, Uncertainty, Compton & X-Rays