- 1(current)
Q. No.The focal length of a glass \((\mu = 1.5)\) lens in air is \(20~\text{cm}.\) If it is dipped in water \(\left(\mu= \frac{4}{3}\right)\) its focal length in water will be:
| 1. | \(80~\text{cm}\) | 2. | \(40~\text{cm}\) |
| 3. | \(60~\text{cm}\) | 4. | \(20~\text{cm}\) |
Subtopic: Â Lens Makers' Formula |
 67%
From NCERT
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NEET 2026 - Target Batch - Vital
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A plane-convex lens fits exactly into a plano-concave lens. Their plane surfaces are parallel to each other. If lenses are made of different materials of refractive indices \(\mu_1\) and \(\mu_2\) and \(R\) is the radius of curvature of the curved surface of the lenses, then the focal length of the combination is:
| 1. | \(\frac{R}{2(\mu_1+\mu_2)}\) | 2. | \(\frac{R}{2(\mu_1-\mu_2)}\) |
| 3. | \(\frac{R}{(\mu_1-\mu_2)}\) | 4. | \(\frac{2R}{(\mu_2-\mu_1)}\) |
Subtopic: Â Lens Makers' Formula |
 61%
From NCERT
NEET - 2013
To view explanation, please take trial in the course.
NEET 2026 - Target Batch - Vital
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To view explanation, please take trial in the course.
NEET 2026 - Target Batch - Vital
- 1(current)
Q. No.
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