Question

A concave mirror produces a real image 10mm tall, of an object 2.5mm tall placed at 5cm from the mirror. Calculate focal length of the mirror and the position of the image?

Answer 1

Answer:

A concave mirror produces a real image which is 10mm tall.

So, let h'= -10mm.

The object whose image has been produced is 2.5mm tall.

So, let h= 2.5mm.

The object is placed at 5cm from the mirror.

So, u= -5cm.

Now, converting -10mm to cm we get -1cm, and 2.5mm to cm we get, 0.25cm.

So, by the formula of magnification:

m= h'/h= -(v/u)

-1/0.25= -v/ -5

-v= 5/0.25

v= -20

Hence the distance of the image is 20cm.

Now using the formula of mirror:

1/f= 1/v+1/u

1/f= 1/-20 + 1/-5

1/f= -5/20

f= -4

Hence the focal length is 4cm and the image formed is real.

Answer 2

Answer:

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