Question

An object is place at a distance of 20cm in front of a concave lens of focal length of 20cn find the position of the image

Answer 1

Answer:

Dear Student,

Please find below the solution to the asked query:

Mirror formula is given as

1/f = 1/v + 1/u

where

f = focal length = -10 cm

v = image distance = to be found...

u = object distance = -15 cm

so,

-(1/10) = -(1/60) + 1/v

or 1/v = -1/60 + 1/10

or 1/v = (60 - 10)/ (60x 10) = 5/60=1/12

or the image distance is of the distance where the screen should be placed will be

v = 12 cm

now,

the magnification formula is

m = -v/u = hi/ho

or hi = (-v/u) X ho

or hi = -(-12/-60) X 5 (height of the image)

so,

hi = -1cm

Answer 2

Answer:

We can see Object distance (u) is 20cm.

Focal length (f)= 15 cm.

By using sign convention, in concave mirror,

u and f both -(ve)

There is a formula 1/u+1/v=1/f

Buy using this formula we can find the v.

v= 1/f-1/

v=-1/15 - 1/20

V= -60cm

So we can now say that the position of the image will be 60 cm from the mirror

To identify the nature of the image, we have to use the formula of magnification (m)

m= hi/ho=-v/

If it is +(ve) then image will be virtual and erect and vice versa.

m=-(-60)7-20

m= -3

So nature of the image is Real and Inverted.

Explanation: