Question

An object is placed at a distance of 60cm form a concave lens of focal length 30cm use a lens formula to find the distance of the image from the lens list four characteristics of the image (nature position size erect/ inverted ) formed by the lens in the care

Answer 1

Formula to be used:

1/v-1/u=1/f

v--)position the image from the lens

u--)position of the object from the lens

f--)focal length of the given lens.

v,u, f should be substituted according to the sign conventions.

anything which is infront of the lens will taken with -ve sign convention and anything behind the lens will be take with +ve sign.

Remember:

u---> will be always negative for both concave and convex  lens as object is always kept before the lens in normal case.

f--> -ve for concave lens

      +ve for convex lens

Acc to the que.

u= -60cm

f= -30cm

sub the given data,

1/v-(-1/60)= -1/30

1/v+1/60= -1/30

1/v= -1/30-1/60

1/v= -3/60

1/v -1/20

therefore,

v= -20cm

-ve indicates that image formed is real and erect

Note: if u get v in +ve then the image will be virtual and inverted.