Question

A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it where is the needle placed in front of convex lens if the image is equal to the size of the object also find the power of the lens. ​

Answer 1

Yeah ❗

Here's your answer;

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V = 50cm

m = 1

u= ?

P = ?

A convex lens forms a real and inverted image equal to the size of the object if the object is placed at the centre of curvature that is at 2f from the lens .

Therefore, u = v = 50cm

2f = 50cm

f = 25 cm= 0.25m

P = 1/f

= 1/-2

= -0.5D

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Answer 2

Hey Happy Soul ❤

Your Answer :

The position of image should be at 2F, since the image is real and same size.

It is given that the image of the needle is formed at a distance of 50 cm from the convex lens.

Therefore, the needle is placed in front of the lens at a distance of 50 cm.

Focal length :

Object distance (u) = - 50 cm

Image distance, (v) = 50 cm

Focal length = f

According to the lens formula,

1/v - 1/u = 1/f

1/f = 1/50 - 1/(-50)

1/f = 1/50 + 1/50

1/f = 1/25

f = 25 cm = 0.25 m

Power of lens :

p = 1 / f ( in meter)

p = 1/0.25 = +4 D

Hope this will helps you ☺

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