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.

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:

If the critical angle for total internal reflection from a medium to vacuum is \(45^{\circ}\), the velocity of light in the medium is: 

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:

Suppose that the lower half of the concave mirror’s reflecting surface in the given figure is covered with an opaque (non-reflective) material. What effect will this have on the image of an object placed in front of the mirror?

A magnifying glass is used, as the object to be viewed can be brought closer to the eye than the normal near point. This results in: 

(a) a larger angle to be subtended by the object at the eye and hence, viewed in greater detail.
(b) the formation of a virtual erect image.
(c) increase in the field of view.
(d) infinite magnification at the near point.

1. (a, b)
2. (a, c)
3. (b, d)
4. (c, d)

Between the primary and secondary rainbows, there is a dark band known as Alexandar's dark band. This is because:

(a) light scattered into this region interfere destructively
(b) there is no light scattered into this region
(c) light is absorbed in this region
(d) angle made at the eye by the scattered rays with respect to the incident light of the sun lies between approximately 42$°$ and 50$°$

1. (a, c)
2. (a, d)
3. (b, d)
4. (c, d)

A rectangular block of glass ABCD has a refractive index of 1.6. A pin is placed midway on the face AB as shown in the figure. When observed from the face AD, the pin shall:

1. appear to be near A

2. appear to be near D

3. appear to be at all the centre of AD

4. not be seen at all

Consider an extended object immersed in water contained in a plane trough. When seen from close to the edge of the trough, the object looks distorted because:

(a) the apparent depth of the points close to the edge are nearer the surface of the water compared to the points away from the edge
(b) the angle subtended by the image of the object at the eye is smaller than the actual angle subtended by the object in the air
(c) some of the points of the object far away from the edge may not be visible because of total internal reflection
(d) water in a trough acts as a lens and magnifies the object

1. (a, b, c)
2. (a, c, d)
3. (b, c, d)
4. (c, d)

There are certain materials developed in laboratories that have a negative refractive index (figure). A ray incident from the air (medium-\(1\)) into such a medium (medium-\(2\)) shall follow a path given by:

1.
2.
3.
4.