Lens Behavior in Different Media – Rankers Physics

Lens Makers Formula/ Len's Formula: Practice Problem & Solution

Assertion (A): A convex lens of glass \((\mu = 1.5)\) behaves as a diverging lens when immersed in a medium of refractive index \(\mu = 1.65\). Reason (R): A diverging lens is thinner in the middle and thicker at the edges.  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Solution Explained:

To solve this problem, we apply the core principles of Lens Makers Formula/ Len's Formula. Understanding the underlying formula is key to arriving at the correct answer below:

Assertion A is true; if \(mu_{medium} > \mu_{lens}\), a convex lens becomes diverging due to sign change in the lens maker's formula. Reason R is true as it describes a typical concave (diverging) lens shape. But the shape of a diverging lens does not explain the behavioral change of a convex lens.

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Similar Practice Questions

Explore conceptually related problems to test your knowledge.

1. Two transparent media A and B are separated by a plane boundary. The speed of light in those media are $1.5 \times 10^8 m/s$ and $2.0 \times 10^8 m/s$, respectively. The critical angle for a ray of light for these two media is: (2022)
2. Assertion (A): In a magnifying glass, the angle subtended by an object at the eye is equal to the angle subtended by its virtual image at the eye. Still the magnifying glass provides angular magnification. Reason (R): Magnifying glass produce a virtual magnified image of the object.  
3. Assertion (A): When an object is placed between two plane parallel mirrors, all the images formed are of equal intensity. Reason (R): In above situation of two plane parallel mirrors, only two images are possible.  
4. Assertion (A): When a light wave travels from a rarer to a denser medium, it loses energy. Reason (R): When a light wave travels from a rarer to a denser medium, it loses speed and energy carried by the wave is proportional to its speed.  
5. Assertion (A): The image focus (\(2^{\text{nd}}\) focus) and the object focus (\(1^{\text{st}}\) focus) are on the opposite side of the biconvex or biconcave lens. Reason (R): The radii of curvature of a biconvex lens and biconcave lens are on the opposite side of the lens.