A lens forms the image of an object placed at a distance of 45 cm from it on a screen placed at a distance 90 cm on other side of it. (a) Name the kind of lens. (b) Find : (i) the focal length of lens, and (ii) the magnification of image.

Open in App

Solution

(a)
As the image is formed on the other side of the lens the image is real .Hence the lens is a convex lens
(b)
(i)Lens formula is
1/f=1/v-1/u
1/f=1/90-1/-45
1/f=3/90
f=30 cm

(ii)
For a lens , magnification is
m=v/u
m=90/-45
m=-2

Suggest Corrections

Similar questions

Q. An object placed

45 c m

from a lens forms an image on a screen placed

90 c m

on other side of the lens Identify the type of the lens and find its focal length

A lens forms an image of an object which is placed at a distance 15 cm in front of it. if the image forms at a distance 60 cm on the same side Find : (i) the focal length, (ii) the magnification, and (iii) the nature of image.

Q. An illuminated object lies at a distance 1.0 m from a screen. A convex lens is used to form the image of the object on a screen placed at a distance 75 cm from the lens. Find :
1) the focal length of lens
2) the magnification.

Q. An illuminated object lies at a distance 1.0 m from a screen. A convex lens is used to form the image of object on a screen placed at distance 75 cm from the lens. Find : (i) the focal length of lens, and (ii) the magnification.

If an object is placed at 60 cm before lens I focal length of lens I is 30 cm and focal length of lens II is 45 cm., find out the image distance formed by lens II from O.

Join BYJU'S Learning Program

A lens forms the image of an object placed at a distance of 45 cm from it on a screen placed at a distance 90 cm on other side of it. (a) Name the kind of lens. (b) Find : (i) the focal length of lens, and (ii) the magnification of image.

(a) As the image is formed on the other side of the lens the image is real .Hence the lens is a convex lens (b) (i)Lens formula is 1/f=1/v-1/u 1/f=1/90-1/-45 1/f=3/90 f=30 cm (ii) For a lens , magnification is m=v/u m=90/-45 m=-2

(a)
As the image is formed on the other side of the lens the image is real .Hence the lens is a convex lens
(b)
(i)Lens formula is
1/f=1/v-1/u
1/f=1/90-1/-45
1/f=3/90
f=30 cm

(ii)
For a lens , magnification is
m=v/u
m=90/-45
m=-2