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

B) The magnification produced by a mirror is +1. What does this mean..?


Equivalent power= sum of individual powers. And P=1/f. Power of combination = 0, focal length = infinity. Magnification (linear) is ratio of image size to the object size (considering their signs). Here, magnification is +1 it means size of image is same as size of object, erect image is formed and image is virtual.
0 0 0
can get the steps involved in getting pwer, focal length n magnification
Power of first lens is +12.5D
power of 2nd lens is -12.5
We know that P=P1+P2
total power = OD
lens will behave as plane glass
focal length of plane glass is always infinite

B)m=+1 signify that image will formed virtual and erect
2 4 2
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