Question

A convex lens produces a real inverted image 2.0 times magnified at a distance of 20cm from the lens. Calculate the focal length of the lens

Answer 1

Answer:

F = 6.67 cm.

Explanation:

m = -2

v = +20cm

f = ?

m = v/u

-2 = 20/u

u = 20/-2 = -10 cm.

Now, by using lens formula,

1/v - 1/u = 1/f

1/20 - 1/-10 = 1/f

1/20 + 1/10 = 1/f

Now taking LCM, we get:

1+2/20 = 1/f

3/20 = 1/f

20/3 = f

6.67cm = f.

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