Question

A convex lense of focal length 20 cm produces a real image of an object , when it is 30 away . Find position and magnification of image ?​

Answer 1

Answer:

Explanation:

Given,

Focal length, f = 20 cm

Object distance, u = - 30 cm

To Find,

Position and magnification of the image.

Formula to be used,

Lens formula, 1/f = 1/v - 1/u

Magnification, m = v/u

Solution,

Putting all the values, we get

1/f = 1/v - 1/u

⇒ 1/v = 1/f + 1/u

⇒ 1/v = 1/20 - 1/30

⇒ 1/v =  3 - 2/60

⇒ 1/v = 1/60

⇒ v = 60 cm

Hence, the image is formed at 60 cm from the lens.

Now, magnification,

Magnification, m = v/u

⇒ m = 60/- 20

⇒ m = - 3 cm

Hence, the magnification is - 3 cm.

And the nature of the image is real and inverted.

Answer 2

Answer:

Given :-

A convex lense of focal length 20 cm produces a real image of an object , when it is 30 away when it is 30 away

To Find :-

Position

Magnification

Solution :-

We know that

1/v = 1/f + 1/u

1/v = 1/20 - 1/60

1/v = 3 - 2/60

1/v = 1/60

On reciprocal we get

v = 60 cm

Now

m = v/u

m = (60)/-20

m = -60/20

m = -3

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