Two plane mirrors and are mounted in a periscope‐like device such that is vertical…

PHYSICS · Subjective · AP · Physics 2: Algebra-based · Geometric Optics · Geometric Optics

Problem

Two plane mirrors

M_{1}

and

M_{2}

are mounted in a periscope‐like device such that

M_{1}

is vertical while

M_{2}

is inclined at

60^{\circ}

M_{1}

. A narrow light beam travelling horizontally from left to right strikes

M_{1}

at point A where the angle of incidence is

30^{\circ}

. (a) Draw a clear, labelled ray diagram tracing the path of the beam after successive reflections from

M_{1}

and

M_{2}

until it emerges from the device. (b) Calculate the angle of reflection at

M_{1}

and hence determine the direction of the beam as it moves toward

M_{2}

. (c) Find the angle of incidence at

M_{2}

. (d) Prove that the total deviation produced by the two reflections is

120^{\circ}

, and state whether the emergent beam finally travels upward, downward, or remains horizontal relative to its original direction.