Question

In the figure is shown a concave mirror. A is a point on the principal axis. If an object O is kept at A, image is formed on A itself. Copy the diagram. Draw the image in the diagram. Is the image real or virtual?

Measure the distance PA and write it in the diagram. What is the distance PA called?
Mark a point B on the principal axis, at which, if a point source of light is kept, the rays travel parallel to principal axis after reflection from M. What is point B called?

Answer 1

As the object is placed at A and its image is also formed at A, so the object must be at the center of curvature (C).

PA is called the radius of curvature and on measuring PA = 4.8 cm. Point B marked on the principal axis is called the principal focus.