Question

One half of a convex lens of focal length 10 cm is covered with a black paper . Can such a lens produce an image of a complete object placed at a distance of a complete object placed at a distance of 30 cm from the lens ?Draw a ray diagram to justify your answer .
A 4 cm tall object is placed perpendicular to the principal axis of as convex lens of focal length 20 cm . The distant of the object from the lens is 15 cm Find the nature , position and size of the image .​

Answer 1

Explanation:

Given , f = 20cm

height of u = 4 cm

u = 15cm

we know that ,

1/f = 1/v - 1/u

1/20 = 1/v + 1/15

1/v = 1/20 - 1/15

1/v = 3 - 4 / 60

1/v = -1/60

v = -60

Now, m =

v/u = hi/ ho

60/15 = hi/4

4 = hi/4

hi = 4×4

hi = 16 cm

Hence ,

v = -60cm

height of image is 16

And image is virtual

Hope it helps...