Home
Class 12
PHYSICS
A thin converging lens with focal length...

A thin converging lens with focal length `f = 25 cm` projects the image of an object on a screen removed from the lens by a distance `l == 5.0 m`. Then the screen was draws closer to the lens by a distance `Delta l = 18 cm`. By what distance should the object be shifted for its image to become sharp again ?

Text Solution

Verified by Experts

Since the image is formed on the screen, it is real, so for a conbersing lens object is in the incident side.
Let `s_(1)` and `s_(2)` be the magnitudes of the object distance in the first and second case respectively.
We have the lens formula
`(1)/(s') - (1)/(s) = (1)/(f)` (1)
In the first case from Eqn. (1)
`(1)/((+l)) - (1)/((-s_(1))) = (1)/(f)` or, `s_(1) = (f(l))/(l - f) = 26.31 cm`.
Similarly from Eqn. (1) in the second case
`(1)/((l - Deltal)) - (1)/((-s_(2))) = (1)/(f)` or, `s_(2) = (lf)/((l - Deltal)- f) = 26.31 cm`.
Thus the sought distance `Deltax = s_(2) - s_(1) = 0.5 mm~~ lf^(2) //(l - f^(2))`
Promotional Banner

Topper's Solved these Questions

  • OPTICS

    IE IRODOV, LA SENA & SS KROTOV|Exercise Interference Of Light|33 Videos

  • OPTICS

    IE IRODOV, LA SENA & SS KROTOV|Exercise Diffraction Of Light|60 Videos

  • MECHANICS

    IE IRODOV, LA SENA & SS KROTOV|Exercise Mechanics Problems|92 Videos

  • OSCILLATIONS AND WAVES

    IE IRODOV, LA SENA & SS KROTOV|Exercise Electromagnetic Waves, Radiation|36 Videos

Similar Questions

Explore conceptually related problems

A thin converging lens of focal length f = 25 cm forms the image of an object on a screen placed at a distance of 75 cm from the lens. Now the screen in moved closer to the lens by a distance of 25 cm. The distance through which the object has to be shifted so that its image on the screen is sharp again is

A thin converging lens of focal length f=25.0 cm forms the image of an object,on the screen,at a distance 5m from the lens. The screen is then drawn closer by a distance of 18cm. By what distance should the object be shifted so that its image on the screen is sharp again?

A thin converging lens of focal length 25.0cmforms the image of an object, on the screen, at a distance 5m from the lens. The screen is then drawn closer by a distance of 18cm. By what distance should the object be shifted so that its image on the screen is sharp again?

A converging lens has a focal length of 0.12 m. To get an image of unit magnification the object should be placed at what distance from the converging lens ?

A convex lens of focal length 16 cm forms a real image double the size of the object. The image distance of the object from the lens is

A converging lens of focal length 5 cm is placed at a distance of 20 cm from a screen. How far from the lens should an object be placed so as to form its real image on the screen?

A convex lens is used to obtain a magnified image of an object on a screen . The object is at a distance 10 m from the lens . If the magnification is 19. the focal length of the lens is

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.