如附圖所示,若將甲,乙,丙三種透鏡與直尺的距離縮短相同的距離時,則所成的像一定會變大的有那些?

(1) Based on equations

p = Object distance, q = Image distance, f = Focus

M = Magnification = q/p

Equation: 1/p + 1/q = 1/f => M + 1 = q/f

Set f1 > f2

=> M1 > M2

=> q1/p > q2/p

=> q1 > q2


M = q/f - 1

=> M1 > M2

=> q1/f1 > q2/f2

=> q1*f2 > q2*f1


q1 > q2

=> f2 > f1

=> Answer = 丙



(2) Based on planar glass

Limit(f→∞)Lens = Planar Glass ==> magnification = 0

Thus the larger focus the lesser magnification.

Answer = 丙