Question

Fill in the blanks in the following:
(a) A person $1$m in front of a plane mirror seems to be __________ m from his image.
(b) If you touch your _______ ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with __________.
(c) The size of the pupil becomes __________ when you see in dim light.
(d) Night birds have _________ cones than rods in their eyes.

Answer 1

(a) A person 11m in front of a plane mirror seems to be $2m$ from his image.

Distance between mirror and object $d_1=1m$

Hence, distance between mirror and image $d_2=1m$

Image formed by the plane mirror is behind the mirror. Hence, distance between object and image, $d=d_1+d_2$

$d=1+1=2m$

(b)

If you touch your $\text{left}$ ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with $\text{left hand}$.

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 $\text{large}$ 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 $\text{less}$ 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.