Question

An object 20 cm from a spherical mirror gives rise to virtual image 15 cm behind the mirror. Determine the magnification of the image and the type of mirror used. 

Answer 1

Given,
The distance of the object 'u' = -20 cm

Distance of the virtual image 'v' = 15 cm

We have to find the magnification 'm'.
Using the magnification formula, we get  

`m=-v/u` 

`m=(-15)/-20`  

`m=0.75` 

Thus, the image is virtual, erect and smaller in size.  
The mirror used here is convex, as it forms a smaller virtual image