Two parallel plane mirrors are 30 cm apart. An object is 8 cm from the left mirror. Starting with reflection in the left mirror and then alternating mirrors, find the distance in centimetres between the third and fifth image positions.
Physics · Geometrical optics · law of reflection and plane mirror
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Question

Two parallel plane mirrors are 30 cm apart. An object is 8 cm from the left mirror. Starting with reflection in the left mirror and then alternating mirrors, find the distance in centimetres between the third and fifth image positions.

Physics · Geometrical optics · law of reflection and plane mirror

G1 Physics · Accepted Answer

With mirrors at x=0 and x=30, the sequence is −8, 68, −68, 128, −128. The third and fifth images are at −68 and −128 cm, separated by 60 cm.