Question

an object is placed at a distance of 50 cm from a concave lens the image is formed at a distance of 20 cm from the lens find the focal length of the lens ​

Answer 1

Answer:

here is given

distance of object (u)=-50

distance of the image (v)= 20

focal length (f)=?

as we know that 1/v-1/u=1/f

so , 1/20+1/50= 1/f

=>5+2/100=1/f

=>7/100=1/f

=>100/7=f

=>14.3=f

=>f=14.3

so the focal length is 14.3cm