Question

an object is placed at a distance 20cm from a convex lens of focal length 10cm.find the image distance and nature of the image​

Answer 1

Image distance is 20 cm and it is real and inverted.

Explanation:

It is given that,

Object distance from the convex lens, u = -20 cm

Focal length of the convex lens, f = +10 cm

If v is the position of image with respect to the mirror. It can be calculated using lens formula as :

\dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}

f

1

=

v

1

−

u

1

\dfrac{1}{v}=\dfrac{1}{f}+\dfrac{1}{u}

v

1

=

f

1

+

u

1

\dfrac{1}{v}=\dfrac{1}{10}+\dfrac{1}{(-20)}

v

1

=

10

1

+

(−20)

1

v = 20 cm

So, the image will be formed at a distance of 20 cm behind the lens. If m is the magnification of the lens,

m=\dfrac{v}{u}m=

u

v

m=\dfrac{20}{-20}m=

−20

20

m = -1 (image is real and inverted)

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Answer 2

Answer:

,

object distance=-20cm=u

focal length=10cm

image distance=v=?

Now,

From lens formula:1/v-1/u=1/f

1/v-1/(-20) =1/10

1/v=1/10-1/20

1/v=2-1/20

1/v=1/20

Therefore,v=20cm and nature of image is {Real and inverted}