Question

In the List-I, four optical effects are mentioned. The physical phenomena of light which are essential to describe these optical effects are given in List-II. Choose the option which describes the correct match between the entries in List-I to those in List-II. {p{7cm} p{6cm}} List-I & List-II
(P) Colorful sky in north polar region (Aurora Borealis) & (1) Dispersion and reflection
(Q) Partially polarized sunlight & (2) Total internal reflection
(R) Rainbow & (3) Diffraction
(S) Dark and bright fringes & (4) Scattering of light by molecules in the atmosphere
& (5) Emission of radiation from oxygen and nitrogen atoms excited by charged particles

• A. \(P \to 5,\ Q \to 4,\ R \to 1,\ S \to 3\)
• B. \(P \to 4,\ Q \to 2,\ R \to 1,\ S \to 3\)
• C. \(P \to 4,\ Q \to 1,\ R \to 2,\ S \to 3\)
• D. \(P \to 5,\ Q \to 4,\ R \to 1,\ S \to 2\)

Hint:

Aurora Borealis: \[ \text{Emission from excited atmospheric atoms} \] Rainbow: \[ \text{Dispersion + internal reflection} \] Fringes: \[ \text{Interference/Diffraction} \]

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
This question tests the qualitative understanding of common natural optical phenomena and their physical basis. Most of these effects result from the interaction of light with the atmosphere or specific geometric configurations.
Step 3: Detailed Explanation:
(P) Colorful sky in north polar region (Aurora Borealis): This phenomenon is caused by the interaction of solar wind particles with the Earth's magnetic field, which directs them to the poles. These high-energy particles excite oxygen and nitrogen atoms in the atmosphere. When these atoms de-excite, they emit characteristic radiation. Thus, it matches (5) "Emission of radiation from excited atoms".
(Q) Partially polarized sun light: When unpolarized sunlight enters the atmosphere, it is scattered by gas molecules and small particles. Rayleigh scattering causes the scattered light to become partially polarized, especially when viewed at \( 90^{\circ} \) to the sun's direction. Thus, it matches (4) "Scattering of light by molecules in the atmosphere".
(R) Rainbow: A primary rainbow is formed by the dispersion of sunlight as it enters a raindrop, followed by one internal reflection, and finally dispersion again as it exits. Thus, the essential phenomena are dispersion and reflection. Matches (1).
(S) Dark and bright fringes: These are the result of the superposition of waves, leading to constructive and destructive interference. This is typically observed in diffraction and interference experiments. Matches (3) "Diffraction".
Step 4: Final Answer:
Matching each effect to its fundamental physical cause leads to the combination in option (A).