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Q. No.The refractive index of a material of a plano-concave lens is \(\dfrac{5}{3},\) and the radius of curvature is \(0.3\) m. The focal length of the lens in air is:
1. \(-0.45\) m
2. \(-0.6\) m
3. \(-0.75\) m
4. \(-1.0\) m
1. \(-0.45\) m
2. \(-0.6\) m
3. \(-0.75\) m
4. \(-1.0\) m
Subtopic: Lens Makers' Formula |
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A convex lens is made of a material having refractive index \(1.2.\) Both the surfaces of the lens are convex. If it is dipped into water (\(\mu=1.33 \) ), it will behave like:
| 1. | a convergent lens | 2. | a divergent lens |
| 3. | a rectangular slab | 4. | a prism |
Subtopic: Lens Makers' Formula |
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When a biconvex lens of glass having a refractive index of \(1.47\) is dipped in a liquid, it acts as a plane sheet of glass. The liquid must have a refractive index:
| 1. | equal to that of glass. |
| 2. | less than one. |
| 3. | greater than that of glass. |
| 4. | less than that of glass. |
Subtopic: Lens Makers' Formula |
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AIPMT - 2012
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If a plano-convex lens has a radius of curvature of \(10~\text{cm}\) for its convex surface and a focal length of \(30~\text{cm},\) what is the refractive index of the lens material?
1. \(1.50\)
2. \(1.66\)
3. \(1.33\)
4. \(2.50\)
1. \(1.50\)
2. \(1.66\)
3. \(1.33\)
4. \(2.50\)
Subtopic: Lens Makers' Formula |
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A plano-convex lens of refractive index \(\mu_1\) and focal length \(f_1\) is kept in contact with another plano-concave lens of refractive index \( \mu_2\) and focal length \(f_2.\) If the radius of curvature of their spherical faces is \(R \) each and \(|f_1|=2|f_2|, \) then \(\mu_1\) and\( \mu_2\) are related as:
1. \(\mu_1+\mu_2=3 \)
2. \(2\mu_1-\mu_2=1 \)
3. \(3\mu_2+\mu_1=1 \)
4. \(2\mu_2+\mu_1=1 \)
1. \(\mu_1+\mu_2=3 \)
2. \(2\mu_1-\mu_2=1 \)
3. \(3\mu_2+\mu_1=1 \)
4. \(2\mu_2+\mu_1=1 \)
Subtopic: Lens Makers' Formula |
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A point object in the air is in front of the curved surface of a plano-convex lens. The radius of curvature of the curved surface is \(30 ~\text{cm}\) and the refractive index of the lens material is \(1.5,\) then the focal length of the lens (in cm) is:
1. \(60~\text{cm}\)
2. \(40~\text{cm}\)
3. \(20~\text{cm}\)
4. \(50~\text{cm}\)
1. \(60~\text{cm}\)
2. \(40~\text{cm}\)
3. \(20~\text{cm}\)
4. \(50~\text{cm}\)
Subtopic: Lens Makers' Formula |
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If a biconvex lens of material of refractive index \(1.5\) has a focal length \(20~\text{cm}\) in air, then its focal length when it is submerged in a medium of refractive index \(1.6\) is:
1. \(-160~\text{cm}\)
2. \(160~\text{cm}\)
3. \(-1.6~\text{cm}\)
4. \(-16~\text{cm}\)
1. \(-160~\text{cm}\)
2. \(160~\text{cm}\)
3. \(-1.6~\text{cm}\)
4. \(-16~\text{cm}\)
Subtopic: Lens Makers' Formula |
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JEE
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