Refraction and Reflection – Ray Diagrams Simulation
What the simulation does
It runs the AQA required practical on light as an interactive 3D bench setup. Pupils choose between two investigations. In Reflection mode, a ray box shines a single ray at a plane mirror, and pupils measure the angle of incidence and the angle of reflection, both from the normal, to confirm that the angle in equals the angle out. In Refraction mode, the ray passes into a glass block, bends toward the normal, travels through the block, then emerges parallel to the original ray with a lateral shift. Pupils measure the angle of incidence and the angle of refraction and then work out the refractive index using n equals sin i divided by sin r, which comes out at about 1.50 for the glass.
The workflow mirrors the real practical step by step: place the optical element, draw the normal, switch on the ray box, set the angle, trace the outgoing ray, then swing a printed protractor over the strike point to read both angles. After the reading, the simulation pauses so pupils can study the setup, and they press Continue when ready to move to the calculation, which checks their answer and diagnoses common mistakes like measuring from the surface instead of the normal, or dividing the wrong way round. A readings table records each trial, and the full accessibility suite is available for pupils who need it.
Suggested class activity
A good lesson is to have pupils build a results table across a range of angles. Ask them to run the refraction investigation at five or six angles of incidence, recording i, r, and sin i divided by sin r each time. The powerful moment comes when they notice that although i and r both change, the ratio of the sines stays fixed at roughly 1.50. That is the refractive index revealing itself as a constant property of the glass, which is exactly the idea the practical is meant to build.
To extend it, pupils can plot sin i on the vertical axis against sin r on the horizontal axis. The points should fall on a straight line through the origin, and the gradient of that line is the refractive index. This links the hands on measurement to graph skills and reinforces that a single trial can be unreliable, whereas a line of best fit through many points gives a far better value.
A quick reflection warm up works well before the refraction task. Give pairs a target such as “predict the reflected angle for 25, 45, and 60 degrees,” let them state their predictions aloud, then run the simulation to confirm the law of reflection holds every time. This front loads the key habit of measuring from the normal, which is the single most common exam error, before they meet the trickier bending in the glass block.
If you want a discussion point to close, ask why the ray leaving the far side of the block ends up parallel to the ray that went in, and what happened to its direction and speed inside the glass. That pushes pupils toward explaining refraction in terms of the light slowing in the denser medium, which is the reasoning examiners look for.