1. | \(2\) | 2. | \(1\) |
3. | No image will be formed | 4. | \(3\) |
1. | infinity | 2. | \(+2\) D |
3. | \(+20\) D | 4. | \(+5\) D |
A concave lens of focal length \(-25\) cm is sandwiched between two convex lenses, each of focal length, \(40\) cm. The power in dioptre of the combined lens would be:
1. | \(55\) | 2. | \(9\) |
3. | \(1\) | 4. | \(0.01\) |
A convex lens A of focal length 20 cm and a concave lens B of focal length 5 cm are kept along the same axis with the distance d between them. If a parallel beam of light falling on A leaves B as a parallel beam, then distance d in cm will be
1. 25
2. 15
3. 30
4. 50
A point object is placed at a distance of \(60~\text{cm}\) from a convex lens of focal length \(30~\text{cm}\). If a plane mirror were put perpendicular to the principal axis of the lens and at a distance of \(40~\text{cm}\) from it, the final image would be formed at a distance of:
1. | \(30~\text{cm}\) from the plane mirror, it would be a virtual image. |
2. | \(20~\text{cm}\) from the plane mirror, it would be a virtual image. |
3. | \(20~\text{cm}\) from the lens, it would be a real image. |
4. | \(30~\text{cm}\) from the lens, it would be a real image. |
A plane-convex lens of unknown material and unknown focal length is given. With the help of a spherometer, we can measure the
1. | focal length of the lens. |
2. | radius of curvature of the curved surface. |
3. | aperture of the lens. |
4. | refractive index of the material. |
The power of a biconvex lens is \(10\) dioptre and the radius of curvature of each surface is \(10\) cm. The refractive index of the material of the lens is:
1. \( \frac{4}{3} \)
2. \( \frac{9}{8} \)
3. \( \frac{5}{3} \)
4. \( \frac{3}{2}\)
A biconvex lens has power \(P.\) It is cut into two symmetrical halves by a plane containing the principal axis. The power of one part will be:
1. \(0\)
2. \(\frac{P}{2}\)
3. \(\frac{P}{4}\)
4. \(P\)