Question

At an instant, a watch shows a time 2:35. Find the time that appears when seen through a mirror.

Answer 1

Hint: The images formed on a plane mirror will be laterally inverted. This suggests that the right side of the object will appear on the left side of the mirror and the left side of the object will appear on the right side of the mirror.

Complete step by step answer:
Step 1: Mention the key features of a plane mirror.
A plane mirror forms virtual and erect images. Also, the images formed will be of the same size as that of the object. The object distance and the image distance will be the same.
Step 2: Sketch the time on the dial of the watch.
The time shown by the dial of the watch is given to be 2:35. This is sketched in the figure given below.

Step 3: Sketch the time on the dial of the watch as seen in the mirror.
Since the plane mirror causes a left-right reversal, the numbers on the right side of the dial i.e., 1, 2, 3, 4, and 5 will now lie on the left of the dial, and the numbers on the left side of the dial i.e., 11, 10, 9, 8 and 7 will lie on the right side of the dial seen in the mirror. The time shown by the mirror is given in the figure below.

So the time seen in the mirror is 9:35.

Note:
Alternate method:
The time seen in the mirror can also be obtained by the relation given by,
${\text{mirror time}} = 11:60 - {\text{actual time}}$
Here, the actual time is $2:35$.
So the time seen in the mirror will be $11:60 - 2:35 = 9:25$.