Question

The image formed is 3 times to the object while using the converging lens,find the focal length of the lens,if object of at 10 cm from the lens​

Answer 1

Explanation:

u =-10 cm

h = h (object)

h= 3h(image)

by magnification

v/u =3h/h=3

.

v =3 x -10 =-30 cm

now focal length by lens formula

we get f = -15cm

Answer 2

Answer:

f=-15cm

Explanation:

u=-10cm m=3

we know that

m=-v/u

3=v/10

v=30cm

now, 1/v+1/u=1/f

or,1/30-1/10=1/f

or,1-3/30=1/f

or,-2/30=1/f

or,-1/15=1/f

finally,f=-15 cm