The distance between two point sources of light is `24cm.` Find out where would you place a converging lens of focal length `9cm,` so that the images of both the sources are formed at the same point.

Options

A. 6cm from `S_(1)`
B. 15 cm from `S_(1)`
C. 10 cm from `S_(1)`
D. 12 cm from `S_(1)`

Answer

a.

Explanation

In this case, one of the image will be real and the other virtual. Let us assume that image os `S_(1)` is real and that of `S_(2)` is virtual.
Applying `(1)/(v)-(1)/(u)=(1)/(f)`
For `S_(1): (1)/(y)+(1)/(x)=(1)/(9)` (i)
For `S_(2): (1)/(y)+(1)/(24-x)=(1)/(9) ` (ii)
Solving Eqs. (i) and (ii), we get
`x=6cm`