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 in size to the object? Also find the power of the lens.

For which position of the object does a convex lens form a virtual and erect image? Explain with the help of a ray diagram.

Draw a ray diagram to show the path of the reflected ray corresponding to an incident ray which is direct towards the principal focus of a convex mirror. Mark on it angle of incidence and the angle of reflection.

Redraw the ray diagram given below in your answer book and completer the path of ray.

An object of height 4.0 cm is placed at a distance of 30 cm from the optical centre‘O’ of a convex lens of focal length 20 cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre ‘O’ and principal focus ‘F’ on the diagram. Also find the approximate ratio of size of the image to the size of the object.

Only one of the following applies to a concave lens. This is:

State whether convex lens has a real focus or a virtual focus.

When we focus sunlight using a convex lens at the tip of a matchstick, what will happen? Why?

Copy and complete the diagram below to show what happens to the rays of light when they pass through the concave lens:

Draw the ray diagram in each case to show the position and nature of the image formed when the object is placed:

(i) In front of a convex lens at F,

(ii) At 3F of a convex lens,

(iii) Between the lens and infinity of a concave lens.