a) The image formed in front of the concave mirror is real, so m is negative,

m = -3, u = -10 cm

As m = -v/u or -3 = -v/-10

v = -30 cm

By mirror formula,

1/f = 1/v + 1/u = 1/-30 + 1/-10 = -4/30

or f = -30/4 = -7.5 cm

Radius of curvature, R = 2f = 2 x (-7.5) = 15cm

a) The image formed in front of the concave mirror is real, so m is negative,

m = -3, u = -10 cm

As m = -v/u or -3 = -v/-10

v = -30 cm

By mirror formula,

1/f = 1/v + 1/u = 1/-30 + 1/-10 = -4/30

or f = -30/4 = -7.5 cm

Radius of curvature, R = 2f = 2 x (-7.5) = 15cm

the above answer is wrong pls check it

Expert Answer:

### Negative sign indicates that the mirror is concave mirror.

The calculations seems to be perfect. And it follows all the conditions as per the given data. If you still have any doubt regarding it you can post the complete question which will give clear idea about what information is actually given and what needs to be calculated.

As the object is placed at 10 cm it means it is between centre of curvature and focus and hence the image must be formed beyond centre of curvature i.e. 30 cm according to given data.

## Concept Videos

### Sign Conventions for Spherical Mirrors and Mirror Formu...

Define New Cartesian Sign convention, object/image distance, mirror formula...

### Magnification by Spherical Mirrors

Define New Cartesian Sign convention, object/image distance, mirror formula...

### Reflection of Light - Exam Decoded

Define New Cartesian Sign convention, object/image distance, mirror formula...

### STUDY RESOURCES

Copyright Notice © 2021 Greycells18 Media Limited and its licensors. All rights reserved.