TwiddleLab / Physics / Light and Sight
Project: Laser Maze
What you will learn
- At every mirror, angle in = angle out. Turn a mirror by x and the beam turns by 2x; at 45° a mirror turns a beam through 90°.
- A tilted glass block shifts a beam sideways without changing its direction: it bends in, then bends back out.
- A colour filter passes one band of white light. Every mirror loses a little light, and the losses multiply.
- A level can be written as code: a grid of numbers, a list of rows.
How the lesson goes
Bend, split and trap a laser. Then build a level your friend can't solve.
Warm-up: two rooms, no hints. Drag the white knob on each mirror to turn it. Fewer moves, more stars.
Predict: where will the beam hit the screen after two mirrors?
The mirrors are fixed. Drag the yellow marker on the white screen, then Check.
With flat mirrors the beam keeps its 30° slope and only flips up or down at each bounce, because angle in = angle out.
Turn the mirror to light the target. The beam turns twice as far as the mirror.
Angles are measured from the laser's direction, anticlockwise.
The gap is off the beam's line. Drag a glass block into the beam to shift it.
The block is tilted. Light bends going in and bends back coming out, so it leaves parallel but shifted.
Build your route: white light in, green light only at the target.
Drag pieces from the box onto the bench and turn the mirrors with their knobs. Filters stand upright: put them across a sideways beam.
Plan before you place: draw the beam's path, then Fire.
The mirrors are set. Draw from the laser to wherever you think the beam goes.
Your friend's level never lights up. Find the wrong piece and tap it.
One piece is a lens where a mirror should be.
Challenge: two routes, two targets. Which one gets more light?
Every mirror keeps 95% of the light that hits it. Tap a route, then Check.
Each mirror passes on 95% of what reaches it, so n mirrors pass on 0.95 to the power n. Two mirrors: 90%. Four: 81%. The path length does not matter here because we treat air as perfectly clear (simplified).
Code: a level is a grid of numbers. Sort the lettered cells.
0 is empty, 1 is a wall, 2 is a mirror. 3 and 4 are the laser and the target.
Each cell becomes one number, each row a list, and the level a list of those rows. A program can then read level[0][2] to find out what is in row 0, column 2.
One piece must turn to light the target. Tap it.
The beam goes up from the bottom mirror. Tilted like \, the top mirror turns it left, off the board. Tilted like /, it turns it right, to the target.
A beam goes right. At what angle to the beam must a mirror sit to send it straight up?
Give the angle between the mirror and the beam, in degrees.
With the mirror at 45° to the beam, the beam meets it 45° from the normal and leaves 45° on the other side: 90° in all.
Your level. Fire the laser, then send it to a friend.
Previous lesson: Light Is One Slice of a Spectrum · Part of the course: Light and Sight
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