Question

a 4.0 cm tall object is placed perpendicular to the principal axis of convex lens of focal lengthe 20cm . if the distance of the object is 30cm from the lens then find the position ,nature,and size of the image and find the magnification​

Answer 1

U=-30cm(sign convention)

F=+20cm(since convex lens)

V=?

Ho=4cm(height of object)

Hi=?(height of image)

By lens formula we have

1/f=1/v-1/u

1/v=1/f+1/u.....(1)

V=uf/u+f(after solving the above equation)

So v=-(30*20) /-30+20

V=-(30*20) /-10

V=60cm.....(2)

By magnification formula we have

m=Hi/Ho=v/u(for lens)

So Hi/4=60/-30

Hi=-8cm

So by negative sign we can conclude that the nature of image is real and inverted

Hi is greater than Ho

So the image is enlarged