Question

Fill in the blanks in the following:

(A) A person \[1\;{\text{m}}\] in front of a plane mirror seems to be .......... \[{\text{m}}\] from his image.
(B) If you touch your .......... ear with your 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 the dim light.
(D) Night birds have .......... cones than rods in their eyes.

Answer 1

HintWhen a person is standing in front of the mirror then a virtual image is obtained behind the mirror. That is at the same distance as the distance between the person and mirror. The cones are more sensitive to the bright light.

Complete step by step answer

Let us consider the given activities,
(A)
 We are given that a person is standing \[1\;{\text{m}}\] of the plane mirror,
Let \[{d_1}\] be the distance between object and mirror, and \[{d_2}\] is the distance between the virtual image and the mirror. And consider \[d\] as the distance between the person and the image behind the mirror.
Calculate the distance between the person and image formed behind the mirror,
\[ \Rightarrow d = {d_1} + {d_2}\]
Now we substitute the value
\[d = 1 + 1\]
After adding the numbers we get
\[d = 2\;{\text{m}}\]
Therefore, the distance is \[2\;{\text{m}}\].

(B)
When we touch our left ear from the right hand in front of a plane mirror then we will see in the mirror that our right ear is touched with the left hand.
This is because the image formed in the mirror is laterally inverted. So, we see that the left hand sees the hand.

(C)
When we see in the dim light, then the pupil of the eye becomes larger in size.
This is because the pupil of the eye adjusts to itself and so that it captures more light in the light and size of the pupil increases.

(D)
The rods are more to dim light and the cones are less sensitive in dim light.
Therefore, the night birds have fewer cones.

Note
When we touch our left side of the object then we see in the mirror that right side touches the object. This is because that image formed is laterally inverted due to which left becomes right side and right side becomes the left side of the object.