A clock hung on a wall has marks instead of numerals on its dial on the adjoining wall there is a plane mirror and the image of the clock in the mirror indicates the time 7: 10. Then the time on the clock is:

Question

A clock hung on a wall has marks instead of numerals on its dial on the adjoining wall there is a plane mirror and the image of the clock in the mirror indicates the time 7: 10. Then the time on the clock is: (A) 7: 10 (B) 4: 50 (C) 5: 40 (D) 10: 7

Tardigrade Admin · Accepted Answer

In a plane mirror the image undegoes depth inversion hence, the time on the image is as much ahead of

12 h 0 min

as the time on actual clock is behind

12 h 0 min

.
Time on the actual clock

= 7 h 10 m

.
Time on the image clock

= (12 h

and

0 min) - (7 h

and

10 min)

∴ 4 h

and

50 min

Q. A clock hung on a wall has marks instead of numerals on its dial on the adjoining wall there is a plane mirror and the image of the clock in the mirror indicates the time $7 : 10$ . Then the time on the clock is:

7 : 10

4 : 50

5 : 40

10 : 7

In a plane mirror the image undegoes depth inversion hence, the time on the image is as much ahead of $12 h 0 min$ as the time on actual clock is behind $12 h 0 min$ .
Time on the actual clock $= 7 h 10 m$ .
Time on the image clock
$= (12 h$ and $0 min) - (7 h$ and $10 min)$
$∴ 4 h$ and $50 min$

Q. A clock hung on a wall has marks instead of numerals on its dial on the adjoining wall there is a plane mirror and the image of the clock in the mirror indicates the time 7:10. Then the time on the clock is: