A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object from the lens ? Draw the ray diagram.

Here, Object distance, u = ? (To be calculated)

Image distance, v =- 10 cm (To the left of concave lens)

Focal length, f =- 15 cm (It is a concave lens)

Now, putting these values in the lens formula:

We get:

Object distance, u = -30 cm

Thus, the object is placed at a distance of 30 cm from the concave lens. The minus sign with object distance shows that the object is on its left side. The diagram is shown as: