Question

A converging lens of focal length 0.18 m is used to produce an image of an object on a screen. If a magnification of 9.0 x is required, calculate the distance from the object at which the screen must be placed.

Answer 1

distance between object and screen is 2 m

Step-by-step explanation:

given data

focal length = 0.18 m

magnification = 9.0 x

to find out

distance from the object

solution

we know that magnification is express as

magnification m =
`(v)/(u)` .............1

here u is distance of object from lens

and v is distance of image from lens

so here

9 =
`(v)/(u)`

v = 9 u ..................2

now we will apply here lens formula that is

`(1)/(f) = (1)/(u) + (1)/(v)` ....................3

put here value f is focal length and v = 9 u

`(1)/(0.18) = (1)/(u) + (1)/(9u)`

solve it we get

u = 0.2

so v = 9 (0.2 )

v = 1.8

so here distance between object and screen is v +u

distance between object and screen = 1.8 + 0.2

distance between object and screen is 2 m