Fill in the blanks in the following. 

(a) A person 1 m in front of a plane mirror seems to be [[1]] m away from his image. 

(b) If you touch your [[2]] ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with [[3]]. 

(c) The size of the pupil becomes [[4]] when you see in dim light. 

(d) Night birds have [[5]] cones than rods in their eyes.

a) Ans: 2 m

A mirror with flat reflecting surface is called a plane mirror. For this mirror the distance of the object from the mirror is the same as the distance of the image from the mirror.

Distance between mirror and object, ${\mathrm{d}}_1=1 \mathrm{m}$

Hence, distance between mirror and image, ${\mathrm{d}}_2=1 \mathrm{m}$
 

Image formed by the plane mirror is behind the mirror. Hence, distance between object and image, 

$\mathrm{d}={\mathrm{d}}_1+{\mathrm{d}}_2$

$\mathrm{d}=1+1=2 \mathrm{m}$

Hence a person 1 m in front of a plane mirror seems to be 2 m from his image.