Question

(a) Give two circumstances in which a concave mirror can form a magnified image of an object placed in front of it. Illustrate your answer by drawing labelled ray diagrams for both.
(b) Which one of these circumstances enables a concave mirror to be used as a shaving mirror?

Answer 1

(a) The two circumstances in which a concave mirror can form a magnified image of an object that is placed in front of it are:

1. When an object is placed between the pole and the focus of a concave mirror, the image formed is virtual, erect and magnified, as shown in the figure. Here, the object AB is placed between the pole and the focus of a concave mirror. Its image A'B' is formed behind the mirror and is virtual, erect and magnified.
2. When an object is placed between the centre of curvature and the focus of a concave mirror, the image formed is real, inverted and enlarged, as shown in figure 2. Here, the object AB is placed between the centre of curvature and the focus of a concave mirror. Its image A'B' is formed beyond the centre of curvature and is real, inverted and enlarged.

(b) From the above mentioned cases, only case 1, where the object is placed between the pole and the focus of a concave mirror, can be used as a shaving mirror. This is because, the image formed is virtual, enlarged and erect.