(a) A person 1m in front of a plane mirror seems to be 2 m from his image.
Distance between mirror and object d1 = 1 m
Hence, distance between mirror and image d2 = 1 m
Image formed by the plane mirror is behind the mirror. Hence, distance between object and image, d = d1 + d2
d = 1 + 1 = 2 m
(b) If you touch your left ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with left hand.
Image formed in the plane mirror is laterally inverted. Hence right ear appears as left ear in the image and the left hand appears as right hand in the image
(c) The size of the pupil becomes large when you see in dim light.
The eye pupil adjusts itself to capture more light in the dark and increases its size
(d) Night birds have less cones than rods in their eyes.
Rods are sensitive to dim light and cones are sensitive to bright light. Since the night birds can see in the night, they have more rods.