Question

4. An object is 10.0 cm to the left of a converging lens with focal length 5.00 cm. A second converging lens with focal length 6.00 cm is located 15 cm to the right of the first lens (a) Find the distance between the original object and the final image. 1 (b) If the object height is 0.5 cm, what is the final image height? (c) Describe the final image in as much detail as possible.

Answer 1

o = 10 cm ; f1 = 5 cm ; f2 = 6 cm ; d = 15 cm

a)we know from lens eqn,

1/f = 1/i + 1/o

i = o x f / (o - f)

i1 = o1 xf1 / (o1 - f1)

i1 = 10 x 5/(10 - 5) = 10 cm

this will serve as the object for other lens, so object distance for other lens will be:

o2 = d - i1 = 15 -10 = 5 cm

i2 = o2 x f2 / (o2 - f2)

i2 = 5 x 6 / (5 - 6) = -30 cm

So the distance between original object and final image is:

D = 10 + 15 + 30 = 55 cm

Hence, D = 55 cm

b)we know that,

M = -i/o = h'/h

-(-30)/10 = h'/0.5 => h' = 1.5 cm

Hence, image height = 1.5 cm

c)The final image will be virtual, upright and magnified.