Question

Consider sunlight incident on a pinhole of width 10³A. The image of the pinhole seen on a screen shall be ______.

1. a sharp white ring.
2. different from a geometrical image.
3. a diffused central spot, white in colour.
4. diffused coloured region around a sharp central white spot.

Options

• a and c

• a and d

• b and d

• b and c

Answer 1

b and d

Explanation:

Diffraction of Light can be observed only if the size of obstacle/aperture is less than the wavelength of light.

Given, width of pinhole = 10³ Å = 1000 Å

We know that wavelength of sunlight ranges from 4000 Å to 8000 Å. Clearly, wavelength X < width of the slit.

Hence, light is diffracted from the hole. Due to diffraction from the slit, the image formed on the screen will be different from the geometrical image.