Why does light refract?

What is the earth's primary source of light energy?

Focal length of plane mirror is

Image formed by plane mirror is

A concave mirror gives real, inverted and same size image if the object is placed

Power of the lens is -40, its focal length is

A concave mirror gives virtual, refract and enlarged image of the object but image of smaller size than the size of the object is

In optics an object which has higher refractive index is called

The optical phenomena, twinkling of stars, is due to

Convex lens focus a real, point sized image at focus, the object is placed

The unit of power of lens is

The radius of curvature of a mirror is 20cm the focal length is

An object is placed 20 cm in front of a plane mirror. The mirror is moved 2 cm towards the object. The distance between the positions of the original and final images seen in the mirror is:

A ray of light that strikes a plane mirror PQ at an angle of incidence of 30^o, is reflected from the plane mirror and then strikes a second plane mirror QR placed at right angles to the first mirror. The angle of reflection at the second mirror is:

Which position of the object will produce a magnified virtual image, if a concave mirror of focal length 15 cm is being used?

A concave mirror produces a magnification of +4. The object is placed:

Two big mirrors A and B are fitted side by side on a wall. A man is standing at such a distance from the wall that he can see the erect image of his face in both the mirrors. When the man starts walking towards the mirrors, he finds that the size of his face in mirror A goes on increasing but that in mirror B remains the same:

A ray of light is travelling in a direction perpendicular to the boundary of a parallel glass slab. The ray of light:

A lens of focal length 12 cm forms an erect image, three times the size of the object. The distance between the object and image is:

If an object is placed 21 cm from a converging lens, the image formed is slightly smaller than the object. If the object is placed at a distance of 19 cm from the lens, the image formed is slightly larger than the object. The approximate focal length of the lens is:

A student does the experiment on tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence. He can get a correct measure of the angle of incidence and the angle of emergence by following the labelling indicated in figure:

A student traces the path of a ray of light passing through a rectangular slab for three different values of angle of incidence (∠i ) namely 30^o, 45^o and 60^o. He extends the direction of incident ray by a dotted line and measures the perpendicular distance ‘l’ between the extended incident ray and the emergent ray.

He will observe that:

Which of the following mirror is used by a dentist to examine a small cavity?

An object at a distance of 30 cm from a

concave mirror gets its image at the same point. The focal length of the mirror is

If a man’s face is 25 cm in front of concave shaving mirror producing erect image 1.5 times the size of face, focal length of the mirror would be

The refractive index of water is 1.33. The speed of light in water will be

You are given three media A, B and C of refractive index 1.33, 1.65 and 1.46. The medium in which the light will travel fastest is