Question

An experiment is conducted in which red light is diffracted through a single slit. Listed below are alterations made, one at a time, to the original experiment, and the experiment is repeated. After each alteration, the experiment is returned to its original configuration.
A. The slit width is halved.
B. The distance between the slits and the screen is halved.
C. The slit width is doubled.
D. A green, rather than red, light source is used.
E. The experiment is conducted in a water-filled tank.
F. The distance between the slits and the screen is doubled.
Which of these alterations decreases the angles at which the diffraction minima appear?

Answer 1

Answer:

B. The distance between the slits and the screen is halved.

C. The slit width is doubled.

D. A green, rather than red, light source is used.

E. The experiment is conducted in a water-filled tank.

Explanation:

As we know that the position of first minimum is given as

$a sin\theta = N\lambda$

so we have

$\theta = sin^{-1}(\fracN\lambda}{a})$

so width of minimum is given as

$w = L\times sin^{-1}(\fracN\lambda}{a})$

now if we need to decrease the angular position of minimum

1). so we can decrease the distance of screen from the slit

2). we can decrease the wavelength

3). We can increase the width of the slit

So correct answer will be

B. The distance between the slits and the screen is halved.

C. The slit width is doubled.

D. A green, rather than red, light source is used.

E. The experiment is conducted in a water-filled tank.