When an object is placed at a distance of 36cm from a convex lens, an image of the same size as the object is formed. What will be the nature of image formed when the object is placed at a distance of:

1. 10cm from the lens?
2. 20cm from the lens?

“A ray of light incident on a rectangular glass slab immersed in any medium emerges parallel to itself.” Draw labeled ray diagram to justify this statement.

Identify the device used as a spherical mirror or lens in following cases, when the image formed is virtual and erect in each case.Object is placed between infinity and device, image formed is diminished and between pole and focus, behind it.

Draw a ray diagram showing how a concave mirror can be used to produce a real, inverted and diminished image of an object.

An object is placed at the following distance from a convex lens of focal length 15cm:

1. 35cm
2. 30cm
3. 20cm
4. 10cm

Which position of the object will produce:

1. A magnified real image?
2. A magnified virtual image?
3. A diminished real image?
4. An image of same size as the object?

The boy walks towards the mirror at a speed of 1m/ s. At what speed does his image approach him?

What is meant by power of a lens? What does its sign (+ve or -ve) indicate? State its S.I. unit. How is this unit related to focal length of a lens?

A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?

1. How can you bend light away from the normal?
2. How must light travel out of a substance if it is not going to be refracted?

‘‘A concave mirror of focal length 15cm can form a magnified erect as well as inverted image of an object placed in front of it.’’ Justify this statement stating the position of the object with respect to the pole of the mirror in both cases for obtaining the images.