A compound lens is made of two lenses in contact having powers + 12.5D and - 2.5D. Find the focal length and power of combination.

The magnification produced by a mirror is +1. what does this mean?

 power of combination = 12.5 + (-2.5 )

= 10 D wkt , p = 1/f 

f = 1/P

= 1/10 

f = 0.1 m 

= 0.1 * 100 cm 

= 10 cm ...

therefore , total power is 10 D and focal lenght is 10 cm or 0.1 m 

if m = +1 this means the image formed is of same size of the object .....

hope it helps u