Two transparent media of refractive indices µ1 and µ3 have a solid lens shaped tan parent material refractive index µ2 between them as shown in figures in Column II. A ray traversing these media is also shown in the figures. In Column I different relationships between µ1, µ2 are given. Match them to the ray diagrams shown in Column II.
Column-I | Column-II |
(A) µ1 < µ2 | ![]() |
(B) µ1 > µ2 | ![]() |
(C) µ2 = µ3 | ![]() |
(D) µ2 > µ3 | ![]() |
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For (p) μ2 > μ1
as light rays bend towards normal at first refraction
µ2 = µ3 as no refraction occurs at second refraction
Option : (A), (C)
For (q)
μ2 < μ1 as bend away from normal at first refraction
μ3 < μ2 as bends away from normal at second refraction
Option (B), (D)
For (r)
μ2 > μ1 as bend towards the normal at first refraction
μ2 = μ3 as no refraction occurs at second refraction
Option (A), (C)
For (s)
μ2 < μ1 as bend away from normal at first refraction
μ3 < μ2 as bend away from normal at second refraction
Option (B), (D)
For (t)
μ2 < μ1 as bend away from normal at first refraction
μ2 = μ3 as no refraction occurs at second refraction
Option (B), (C)
This question involves matching refractive index relationships with ray diagrams for a lens system. The key concept is refraction at curved surfaces and how the path of a light ray bends depending on the refractive indices of the media.
When light travels from one medium to another, its path bends. The direction of bending depends on the refractive indices of the two media. The formula governing refraction at a spherical surface is:
Where:
Rule of Thumb for Bending: Light bends towards the normal when it enters a denser medium (higher refractive index) and away from the normal when it enters a rarer medium (lower refractive index).
Step 1: Analyze Condition (A) μ1 < μ2
This means the ray is moving from a rarer medium (μ1) to a denser medium (μ2). Therefore, at the first surface, the ray should bend towards the normal. Look for a diagram where the incident ray, upon entering the lens, bends towards the center of curvature of that surface. This matches the first diagram in Column II.
Step 2: Analyze Condition (B) μ1 > μ2
This means the ray is moving from a denser medium (μ1) to a rarer medium (μ2). Therefore, at the first surface, the ray should bend away from the normal. Look for a diagram where the incident ray, upon entering the lens, bends away from the center of curvature. This matches the second diagram in Column II.
Step 3: Analyze Condition (C) μ2 = μ3
This means the refractive index of the lens material (μ2) is equal to the refractive index of the medium on the right (μ3). There is no refraction at the second surface; the ray will pass through undeviated. The entire deviation happens only at the first surface. The ray inside the lens will be a straight line until the second surface, where it continues straight without bending. This matches the fourth diagram in Column II.
Step 4: Analyze Condition (D) μ2 > μ3
This means the ray inside the lens (μ2) is moving towards a rarer medium (μ3). At the second surface, the ray will bend away from the normal. Look for a diagram where the ray, upon exiting the lens, bends away from the center of curvature of the second surface. This matches the third diagram in Column II.
The fifth diagram shows a ray converging towards the principal axis after refraction, which is a general case and is not exclusively tied to any one specific inequality from Column I. It is often used as a distractor.
Related Topics:
Key Formula (Lens Maker's Formula):
For a lens with radii of curvature R1 and R2, surrounded by a medium of refractive index μ1, the focal length (f) is given by: This formula shows how the power of a lens depends on the ratio of the refractive indices of the lens material and the surrounding medium.