Question

Two convex lenses are placed 15 cm apart. The left lens has a focal length of 10 cm, and the right lens a focal length of 5 cm. An object is 50 cm to the left of the left. lens. Where does the image from the right lens appear? Is this image real or virtual? This setup is essentially a simple telescope, (the shorter focal length lens being the one you look through) so what does your answer tell you about looking at a nearby object through a telescope? (Hint: Treat the image from the left lens as the object for the right lens.)

Answer 1

The image distance from right lens is 2.86 cm and image is real.

Step-by-step explanation:

Given that,

Focal length of left lens = 10 cm

Focal length of right lens = 5 cm

Distance between the lenses d= 15 cm

Object distance = 50 cm

We need to calculate the image distance from left lens

Using formula of lens

`(1)/(v)=(1)/(f)-(1)/(u)`

Put the value into the formula

`(1)/(v)=(1)/(10)-(1)/(-50)`

`(1)/(v)=(3)/(25)`

`v=8.33\ cm`

We need to calculate the image distance from right lens

The object distance will be

`u = 15-8.33 = 6.67\ cm`

Using formula of lens

`(1)/(v)=(1)/(f)-(1)/(u)`

Put the value into the formula

`(1)/(v)=(1)/(5)-(1)/(-6.67)`

`(1)/(v)=(1167)/(3335)`

`v=2.86\ cm`

The image is real.

Hence, The image distance from right lens is 2.86 cm and image is real.