Question

Two horizontal plane mirrors with equal length, L = 1 m, are separated by a distance h. A laser light is incident from the left edge of the bottom mirror and makes an angle of 60° with the horizontal. The beam gets reflected five times from the top mirror before emerging from the right edge of the bottom mirror as shown below. What is the total distance covered by the laser between the two mirrors?

Answer 1

The distance is 10 times length of the beam. The length of the beam is 1 m divided by 5, or 0.2 m as follows from the figure. All triangles are equilateral. Therefore, the length of the laser is

$$L=10·0.2=2\text{ m}.$$