Where should an object be placed in front of a concave mirror of focal length 15 cm to have a magnification of 3 in case of
(a) real image
(b) virtual image ?

Explanation

To solve the problem of finding the object placement in front of a concave mirror for both real and virtual images with a given magnification, we will follow these steps:

### Given:
- Focal length (f) of the concave mirror = -15 cm (negative because it's a concave mirror)
- Magnification (M) = 3 for real image and M = 3 for virtual image

### (a) For Real Image

...