Home
Class 12
PHYSICS
A convex lens is used to throw on a scre...

A convex lens is used to throw on a screen `10 m` from the lens, a magnified image of an object. If the magnification is to be `19`, find the focal length of the lens.

Text Solution

Verified by Experts

Here u = -10 m , m = 19
`therefore " " m = -(v)/(u) implies 19 = (-v)/(-10) implies V = 190` m
Using the formula , `(1)/(f)= (1)/(v) - (1)/(u) implies (1)/(f) = (1)/(190) - (1)/(-10) implies (1)/(f) = (1)/(190) + (1)/(10)`
`implies (1)/(f) = (1 + 19)/(190) implies f = (190)/(20) = 9.5` m
Hence , focal length of lens = 9.5 m
Promotional Banner

Topper's Solved these Questions

  • XII BOARDS

    XII BOARDS PREVIOUS YEAR|Exercise PHYSICS (Theory) [SET -I]|33 Videos

  • XII BOARDS

    XII BOARDS PREVIOUS YEAR|Exercise SET-II, DELHI BOARD|8 Videos

  • XII BOARDS

    XII BOARDS PREVIOUS YEAR|Exercise SET -II|9 Videos

  • SAMPLE PAPER 2019

    XII BOARDS PREVIOUS YEAR|Exercise SECTION D|6 Videos

Similar Questions

Explore conceptually related problems

The distance between an object and its real image formed by a lens is D. If the magnification is m , the focal length of the lens is

A screen beaming areal image of magnification formed by a convex lens is moved through a distance x. The objectis the moved until a new image of magnification is formedon the screen. The focal length of the lens is :

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

In a displacement method using lens, we obtain two images for separation of the lens d. One image is magnified as much as the other is diminshed . If m is the magnification of one image, find the focal length of the lens.

A convex lens of focal length f will form a magnified real image of an object if the object is placed

A convex lens of focal length 30 cm produces 5 times magnified real image of an object. What is the object distance?

An object and the image obtained from the lens are as given above. If the distance between the object and the image is 36 cm and the magnification is -2, find the focal length of the lens and draw the ray diagram to show the position of the lens.

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