Question

Waves, as well as objects, spread out while going through a narrow opening.

a. True

b. False

c. Not enough information

You pass a sound and a light wave through identical single slits whose size is half the wavelength of the light wave. After leaving the slit, the wavefronts of the sound and light waves are respectively:

a. Planar and circular

b. circular and planar

c. Both planar

d. Both circular

How would tripling the size of the slits affect the shape of the wavefronts from the previous question?

a. They remain the same
b. They are changed
c. One is changed, one stays the same
d. Not enough information

If you place a converging lens in front of the light wavefronts from the previous question; the light would move:
a. toward the focus if the wavefronts are planar and away if they are circular
b. toward the focus if the wavefronts are circular and away if they are planar
c. toward the focus in both cases
d. Away from the focus in both cases

Answer 1

1. Objects as of macroscopic dimension unlike waves will not spread out while going through a narrow opening as the size of the opening is not comparable to the planar spacing between the crystal structure of the object.

2. The wavefront for sound wave will be circular but for light wave, it will be planar as the size of the single slit is half the wavelength of the light wave.

3. By tripling the size of the slits the shape of the wavefront changes as the fringe width depends inversely on the width of the slit, and hence it will decrease with increase in size of the slit.

4. A converging lens converges all the waves coming towards itself to the focus in case wavefront are planar but in case of circular, they converges away from the focus.