The focal length of a spherical mirror is : 15 cm. The mirror is probably : (a) concave (b) convex (c) plane mirror (d) none of these

Where do you place the object in front of a convex lens to get a real and equal size image of an object? (a) At the principal focus of the lens, (b) At twice the focal length (c) At infinity (d) Between the optical centre of the lens and the principal focus

The image formed by a concave mirror of an object is found to be virtual, erect and larger than the object. The position of the object will be : (a) Between the principal focus and the center of curvature (b) At the center of curvature (c) Beyond the center of curvature (d) Between the pole and the principal focus of the mirror

Which of the following materials cannot be used to make lenses? (a) Water (b) Glass (c) Plastic (d) Soil

Find the power of a concave lens of focal length 2 m.

A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the lens.