(a) A mobile phone lies along the principal axis of a concave mirror. Show by suitable diagram the formation of its image. Explain, why the magnification is not uniform.
(b) Suppose the lower half of the concave mirror's reflecting surface is covered with an opaque material, what effect this will have on the image of the object ? Explain.

(a) The mobile phone AB is placed longitudinally in front of a concave mirror along its principal axis. The magnification of the image is not uniform. To explain it, let us consider that the nearer end A of mobile phone be placed at a distance x from the mirror and l be the length of mobile phone. Then linear magnification of the mobile end A will be $m_A=\frac{f}{f-u}$ For the other end B of mobile u. = (u + 1). Hence, magnification of the mobile phone end B will be $m_B=\frac{f}{f-(u+1)}=\frac{f}{f-u-l}$ Obviously, $m_A$ and $m_B$ have different values. (b) If the lower half of the concave mirror's refracting surface is covered with an opaque material, a complete image of an object placed in front of it is formed because image formation is independent of the size of the mirror. However, intensity of the image is reduced.