need help really tired

Question

.A lens forms an image 15 away. The object us located 10 cm from the lend. What is the focal length of lens? What type of lens is it?

Answer 1

Use the lens formula.

It is a converging lens.

There are two possible answers.

Real Image

1/O + 1/I = 1/f

1/10 + 1/15 = 1/f

f = 150/25 = 6 cm

 

or

Virtual Image

1/10 + 1/(-15) =1/f

f = 30 cm