Question

An object is held at 30cm in front of a co nvex mirror of focal length 15cm. at what distance from the convex mirror should a plane mirror be held so that images in the two images coincide with each other?

Answer 1

heya friend!!☺☺
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here's your answer!!☺☺

We are given

f = -15 cm(
u = -30 cm

and the image distance will be calculated using

1/f = 1/v + 1/u

or

1/v = 1/f + 1/u

= 1/-15 - 1/30

or

1/v = (-2 - 1)/30 = -3/30

thus, we have

v = -10 cm

now, the image formed would be 30cm behind the convex so the total distance between the object and image will be

= 30cm + 10cm = 40cm.

The plane mirror needs to placed at a distance of 20cm from the object in order for the image to coincide as it will form 20 cm behind it. The total distance would thus have to be 40cm.

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hope it helps you!!☺☺

Answer 2

Answer:

U=-30

f=15

Now use mirror formula,

1/f=1/V+1/U

1/15=1/V+(-1/30)

1/15=1/V-1/30

1/V-1/30=1/15

1/V=1/15+1/30

1/V=2+1/30

1/V=3/30=1/10

V=10

30+ 10=40cm

therefore,plane mirror should be pleased at the distance of 20cm from the object coincide as it will for 20cm behind it