magnification = (40*15)/(2*5) = 60X
Given:
Lens.........diameter ...fl#
eyepiece...2cm............5
objective...40cm........15
focal length of eyepiece = 2*5 = 10cm
focal length of objective = 40*15 = 600cm
magnification = FL obj / FL eyp = 600/10 = 60x
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