Question

Which is used to produce polarised light?

• A. Prism of flint glass
• B. NaCl prism
• C. Nicol prism
• D. Biprism

Hint:

Associate optical devices with their primary functions: - \textbf{Prism} \(\rightarrow\) Dispersion - \textbf{Biprism / Double Slit} \(\rightarrow\) Interference - \textbf{Diffraction Grating} \(\rightarrow\) Diffraction - \textbf{Nicol Prism / Polaroid} \(\rightarrow\) Polarization

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Polarization is the process of restricting the oscillations of a transverse wave (like light) to a single plane. A device that produces polarized light from unpolarized light is called a polarizer.
Step 2: Detailed Explanation:
Let's analyze the given options:
(A) Prism of flint glass: A standard glass prism is used for dispersion, i.e., separating white light into its constituent colors. It does not polarize light.
(B) NaCl prism: A prism made of Sodium Chloride (rock salt) is transparent to infrared radiation and is used in IR spectroscopy, not for polarizing visible light.
(C) Nicol prism: This is a specific type of polarizer made from a calcite crystal. It utilizes the phenomenon of double refraction (birefringence) to separate an incident unpolarized light beam into two rays (ordinary and extraordinary) and then eliminates the ordinary ray through total internal reflection, allowing only the plane-polarized extraordinary ray to pass through.
(D) Biprism: A Fresnel biprism is used to produce two coherent sources of light from a single source to demonstrate interference. It does not polarize light.
Step 3: Final Answer:
The Nicol prism is a device specifically designed to produce plane-polarized light. Therefore, option (C) is correct.