Question

A concave lens focal length is 18cm forms and image 12cm from the

lens. How far is the objects placed from lens. Draw a ray diagram.​

Answer 1

Explanation:

Focal length (f ) = -15 cm

Distance of image (v) = -10 cm

1v–1u=1f

1/u = -(1/10) – (1/- 15)

1/u =1/15 – 1/10

1/u = -0.033

u = -30 cm

so the object is placed 30 cm away from the concave lens.

Ray diagram

Answer 2

Answer:

Focal length (f ) = -15 cm

Distance of image (v) = -10 cm

1/v–1/u=1/f

1/u = -(1/10) – (1/- 15)

1/u =1/15 – 1/10

1/u = -0.033

u = -30 cm

so the object is placed 30 cm away from the concave lens.

Ray diagram in attachment