Atomic Black Box

Fire rays into a hidden box and use their paths as evidence to infer what is inside.

Your Mission

Four particles are hidden inside the box. Fire rays from the edge and use what happens to each ray to work out where the particles are.

Be strategic! Your goal is to locate all four particles using as few rays as possible. Think about which ray will give you the most useful evidence before you fire.

Hit — If a particle is directly ahead of the ray at any point along its path, the ray hits it and stops. This can happen before or after a deflection.

Deflection — A particle diagonally ahead bends the ray 90° away from that particle.

Reflection — The ray returns through the same opening where it entered. This can happen in two ways:

• A particle is diagonally beside the ray right as it enters the box.
• The ray passes between two particles on opposite diagonals, causing it to reverse direction and retrace its path.

Example: if a ray travels between two particles on opposite diagonals, it reverses and goes back the way it came.

→ 1

Arrow points into the box = entry.

1 ←

Arrow points out of the box = exit.

→ 2H

H = this ray hit a particle.

↔ 3R

R = this ray returned through the same opening where it entered.

Build your model as you go. Tap any squares you think could contain particles to mark them with a ?. Mark as many possible locations as you need. As new evidence rules locations in or out, tap squares again to revise your model. When you have narrowed your model to four locations, tap Check My Model.

You’ve fired 8 rays. Do you have enough evidence to propose a model? Try marking your best particle locations before firing more rays.

After you reveal the structure, the paths of the rays you fired are drawn on the board so you can explain the evidence.