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 the convex lens
if the image is equal to the size of the object? Also find the power of the
lens.​

Answer 1

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 ☺

Note : Thanks to my answers n ho ske to follow vi kar lo ❤

Answer 2

$\mathfrak{\huge{\red{\underline{\underline{Answer :}}}}}$

The position of the image should be at 2F since the image is the 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.

Object distance (u) = – 50 cm

Image distance, (v) = 50 cm

Focal length = ( f )

According to the lens formula,

$\frac{1}{v} - \frac{1}{u } = \frac{1}{f}$

$\frac{1}{f} = \frac{1}{50} - \frac{1}{ - 50}$

$= > \frac{1}{50} + \frac{1}{50} = \frac{1}{25}$

$f = 25cm \: = 0.25m \:$

$power \: of \: lens \: = \frac{1}{f(in \: metres \: )} = \frac{1}{0.25} = \: + 4d$

Hope it Helps !!