Question

if the magnification produced by a concave lens is (1/n+1), then the object distance is​

Answer 1

Answer:

Magnification = 1/n.

According to mirror formula, object distance = f(n-1). In terms of the radius of curvature, we can write Object Distance = R/2 (n-1)

Answer 2

Concept:

The lens formula is used to determine the focal length of a given lens in a practical manner. It is mathematically expressed as, 1/f = 1/v - 1/u

Given:

Magnification produced by a concave lens = (1/n+1)

Find:

We need to determine the distance of the object from the lens, u.

Solution:

We have magnification as, m =(1/n+1)

The magnification is equal to the ratio of the image distance to the object distance, (1/n+1) = v/u where, v = image distance and u = object distance

Therefore, image distance becomes, v = u/(n+1)  ------ equation 1

From lens formula we have,

1/f = 1/v - 1/u  --------- equation 2

Substituting the value of v from equation 1 to equation 2

Equation 2 becomes, 1/f = (n+1)/u - 1/u = (n+1-1)/u = n/u

Therfore, f = u/n where f = focal length

Hence, u = nf

Thus, the object distance produced by a concave lens with magnification  (1/n+1) is nf

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