Question

a convex lens is of focal length 20 CM what is its power ?

Answer 1

hey mate !!

here is your answer !!


in the questions focal lengths are given In centimeters . first we calculate the power of the lens . according to questions first we change into meters . because the formula of power in metres .

change in metres

1 cm is equal to 1/100 m

then ,

20cm is equal to 20/100 m = 0.5m

focal length f = 0.5m .

a convex lens have positive length.

now , we putting the value in formula power of Lens is equal to.

P = 1 / f ( in metres)

P = 1/0.5 m

P = 1×10/5

P = + 2 dioptres.(+ 2D)

the power of the convex lens is 2 dioptres.the positive sign in power indicated in convex lens .


be brainly .