Optics Question 518

Question: A plane mirror is approaching you at a speed of $ 10cm/sec $ You can see your image in it. At what speed will your image approach you

[CPMT 1974]

Options:

A) $ 10cm/sec $

B) $ 5cm/sec $

C) $ 20cm/sec $

D) $ 15cm/sec $

Show Answer

Answer:

Correct Answer: C

Solution:

Suppose at any instant, plane mirror lies at a distance x from object.

Image will be formed behind the mirror at the same distance x.

When the mirror shifts towards the object by distance $y$ the image shifts $ =x+y-(x-y)=2y $ .

So speed of image = 2 x speed of mirror



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