If an incident ray passes through the focus, the reflected ray will

An image of an object produced on a screen which is about 36 cm using a convex lens. The image produced is about 3 times the size of the object. What is the size of the object?

If R is the radius of curvature of a spherical mirror and f is its focal length. Then, R=?

10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is

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

The unit of power of lens is

Image formed by plane mirror is

The optical phenomena, twinkling of stars, is due to

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 passes from a medium X to another medium Y. No refraction of light occurs if the ray of light hits the boundary of medium Y at an angle of:

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 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:

An object at a distance of + 15 cm is slowly moved towards the pole of a convex mirror. The image will get