Q. No.An object is placed on the principal axis of a concave mirror at a distance of \(1.5f\) (\(f\) is the focal length). The image will be at:
1.
\(-3f\)
2.
\(1.5f\)
3.
\(-1.5f\)
4.
\(3f\)
If the critical angle for total internal reflection from a medium to vacuum is \(45^{\circ}\), the velocity of light in the medium is:
| 1. | \(1.5\times10^{8}~\text{m/s}\) | 2. | \(\dfrac{3}{\sqrt{2}}\times10^{8}~\text{m/s}\) |
| 3. | \(\sqrt{2}\times10^{8}~\text{m/s}\) | 4. | \(3\times10^{8}~\text{m/s}\) |
For the angle of minimum deviation of a prism to be equal to its refracting angle, the prism must be made of a material whose refractive index:
| 1. | lies between \(2\) and \(\sqrt{2}\) |
| 2. | is less than \(1\) |
| 3. | is greater than \(2\) |
| 4. | lies between \(\sqrt{2}\) and \(1\) |
A rod of length \(10~\text{cm}\) lies along the principal axis of a concave mirror of focal length \(10~\text{cm}\) in such a way that its end closer to the pole is \(20~\text{cm}\) away from the mirror. The length of the image is:
1. \(15~\text{cm}\)
2. \(2.5~\text{cm}\)
3. \(5~\text{cm}\)
4. \(10~\text{cm}\)
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. |
A magician during a show makes a glass lens with \(n=1.47\) disappear in a trough of liquid. What is the refractive index of the liquid?
1. \( 1.47 \)
2. \( 1.33 \)
3. \(0.66 \)
4. \( 1.5\)
Find the value of the angle of emergence from the prism given below for the incidence ray shown. The refractive index of the glass is \(\sqrt{3}\).
1. \(45^{\circ}\)
2. \(90^{\circ}\)
3. \(60^{\circ}\)
4. \(30^{\circ}\)
1. \(50\)
2. \(30\)
3. \(25\)
4. \(15\)
A lens of large focal length and large aperture is best suited as an objective of an astronomical telescope since:
| 1. | a large aperture contributes to the quality and visibility of the images. |
| 2. | a large area of the objective ensures better light-gathering power. |
| 3. | a large aperture provides a better resolution. |
| 4. | all of the above. |
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. |
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