Question

The penetration of light into the region of geometrical shadow is called
A. Polarization
B. Interference
C. Diffraction
D. Reflection

Answer 1

Hint: Region of geometrical shadow means the region where the light rays do not reach. When the light passes through the opening slit of an obstacle, it bends around the corners of an obstacle. When the light bends, it illuminates the region of geometrical shadow.

Complete answer:
Region of geometrical shadow means the region where the light rays do not reach. We know that the light can penetrate the transparent or semi-transparent medium. When the light passes through the opening slit of an obstacle, it bends around the corners of an obstacle.

To answer this question, let’s check every option one by one as follows,
Polarization: We know that the light from the sun or the lamp is unpolarized light. This light is created by the vibrations of charge in various directions. When the light vibrates in a single plane, it is known as polarized light. The process of converting unpolarized light into polarized light is called polarization. The penetration of light into the region of geometrical shadow is not the polarization. Therefore, the option A is incorrect.

Interference: We know that when two light waves superimpose each other, it creates another wave of higher or lower amplitude than that of the incident light wave. This phenomenon we call interference of light. The light waves do not penetrate into the region of geometrical shadow to undergo interference. Therefore, the option B is incorrect.

Diffraction: When the light rays travel through the opening slit, it bends around its corners. This bending of light allows the light to pass through the region of geometric shadow and illuminate the region. Thus, we can say that the penetration of light into the region of geometrical shadow is called diffraction.

Reflection: When the light ray incident on the opaque or semi transparent material, it gets reflected. This does not allow the light into the region of geometrical shadow. Therefore, the option D is incorrect.

So, the correct answer is option C.

Note: The polarization of light may allow the light to enter the geometrical shadow but only in the case where the material is transparent. Students must understand the difference between polarization and diffraction. In diffraction of light, the light does not penetrate through the transparent medium to illuminate the shadow but rather it travels through the small opening and bends to illuminate the maximum area.