Home
Class 11
PHYSICS
A convex lens forms an image of an objec...

A convex lens forms an image of an object on a screen ,The height of the image is`9cm`The lens is now disiplaced between the object on the screen.the height of this image is`4cm`.the distance between the object and the screen is `90cm`

A

The distance between the two positions of the lens is `30cm`

B

The distance of the object from the lens in its first position is`36cm`

C

The height of the object is `6cm`

D

The focal length of the lens is`21.6cm`

Text Solution

Verified by Experts

The correct Answer is:
B,C,D
`h=sqrt(h_(1)h_(2)) rArrh=6cm`
`m=(h_(1))/(h) =(v)/(u) rArr (-9)/(6) =(D-x_(1))/(-x_(1))`
`x_(1)=36cm rArrx_(2)=D-x_(1) rArr x_(2)=54cm`
` d=54-36=18cm`
`f=(D^(2)-d^(2))/(4D) rArr f=(90^(2)-18^(2))/(4xx90)`
`f=((90+18)(90-18))/(4xx90) rArr f=(108xx72)/(4xx90)=(3xx72)/(10)=21.6cm`
Promotional Banner

Similar Questions

Explore conceptually related problems

A convex lens forms an image of an object on a screen. The height of the image is 9 cm . The lens is now displaced until an image is again obtained on the screen. Then height of this image is 4 cm . The distance between the object and the screen is 90 cm.

A convex lens forms a real image of an object for its two different positions on a screen. If height of the image in both the cases be 8 cm and 2 cm , then height of the object is

A convex lens forms an image of an object on a screen 30 cm from the lens. When the lens is moved 90 cm towards the object, then the image is again formed on the screen. Then, the focal length of the lens is

A concave mirror forms an image of 20 cm high object on a screen placed 5.0 m away from the mirror. The height of the image is 50 cm. Find the focal length of the mirror and the distance between the mirror and the object.

An object 2.5 cm high is placed in front of a convex lens of focal length 30 cm. If the height of image formed is 5 cm, find the distance between the object and the image?

An object is placed 12cm in front of a lens to form an image on a screen. The size of the image is twice that of the object. What is the distance between the object and the image?

A convex lens produces an image of a real object on a screen with a magnification of 1/2. When the lens is moved 30 cm away from the object, the magnification of the image on the screen is 2. The focal length of the lens is

A convex lens forms a real image 16 mm long on a screen. If the lens is shifted to a new position without disturbing the object or the screen then again a real image of length 81 mm is formed. The length of the object must be

Try this Material: Convex lens, screen, metre scale, stand for the lens etc. Method: Keeping the screen fixed, obtain a clear image of a distant object like a tree or a building with the help of the lens on the screen. Measure the distance between the screen and the lens with the help of the metre scale. Now tum the other side of the lens towards the screen. Again obtain a clear image of the distant object on the screen by moving the lens forward or backward. Measure the distance between the screen and the lens again. What ls this distance between the lens and the screen called?