Question

image produced by concave mirror is found to be 4 times the size of the object if the distance of the mirror is 20 cm from the object what is its focal length. ?

Answer 1

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HOLA! USER

QUESTION :

✓ image produced by concave mirror is found to be 4 times the size of the object if the distance of the mirror is 20 cm from the object what is its focal length ? ✓

GIVEN : v = 4(u), u = 20 cm.

FIND : focal length

SOLUTION :

here we know the formula =>

=> 1/f = 1/v + 1/u .

=> f = ? , v = 4(u) = 4(20)=80 cm , u = 20cm.

=> 1/f = 1/80 + 1/20

=> 1/f = 1+4/80

=> 1/f = 5/80

=>1/f = 1/16

=> by cross multiplication.

=> 16 = f

=> f = 16 cm