Mirror Maze

Can you bend a laser round corners? Place mirrors on the grid and turn them to steer the beam to the target in five levels.

Level
1 of 5
Mirrors used
0 of 2
Bounces
0
Target
Not yet

The maths, live

Law of reflection angle i = angle rPlace a mirror in the beam
Beam turns by 180° − 2 × iNo bounce yet

Tap a square to place a mirror, tap it again to turn it 45°, and drag it to move it (drag it off the grid to remove it). The dashed line is the normal: the angles either side are always equal.

How it works

When light hits a mirror it bounces off. The normal is an imaginary line at right angles to the mirror. The angle between the incoming ray and the normal is the angle of incidence, and the angle between the outgoing ray and the normal is the angle of reflection.

The law of reflection says these two angles are always equal. A mirror turned at 45° to the beam reflects it at 45° on the other side of the normal, so the beam turns through a right angle. A mirror square-on to the beam sends it straight back.

Try this

  1. Solve each level using the fewest mirrors you can.
  2. Turn a mirror so the beam comes straight back. What is the angle of incidence?
  3. Show all the angles. Is the angle in always the same as the angle out?