JAMB - Physics (2004 - No. 37)
If u is the object distance and v the image distance, which of the following expressions gives the linear magnification produced by a convex lens of focal length f?
u/f - f
u/v + f
v/f + 1
v/f - 1
Explanation
Magnification, M = v/u = v (1/u)
And for the Lens formula 1/u + 1/v = 1/f
=> 1/u = 1/f - 1/v
∴M = V(1/u)
= V(1/f - 1/v) = v/f - v/v = v/f - 1
∴M = v/f - 1
And for the Lens formula 1/u + 1/v = 1/f
=> 1/u = 1/f - 1/v
∴M = V(1/u)
= V(1/f - 1/v) = v/f - v/v = v/f - 1
∴M = v/f - 1
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