Ray boxes and plane mirrors: function, alignment and handling

A ray box produces a visible light path across a surface. Its slit helps select a narrow beam. A plane mirror changes the path by reflection, while its holder maintains the reflecting surface's position. A correct angle comparison needs those parts to stay aligned.

This guide covers the supplied non-laser ray-box arrangement. Follow the actual manufacturer's supply instructions and the trainer's working position; a laser is a different source with different controls.

Form a ray you can mark

IOP's reflection activity uses a single visible streak, a supported mirror and an angle reference. The source's voltage and lamp specification are examples, not values to transfer to a different product.

Observe the streak on the paper instead of looking into the source. Direct it across the assigned work surface and keep its reflection away from people. A broader streak is not a sharper direction measurement; mark the agreed centre consistently.

Align the reflecting surface

The face of glass and the reflecting coating need not occupy the same plane. Ask which surface the actual mirror uses and align it to the recorded mirror line. A second faint reflection is not permission to choose whichever line makes the angles match.

Use the assigned holder and check for chips, cracks or movement. Do not balance the mirror on an unsuitable edge or press against it while placing a protractor. Broken glass needs the trainer's collection procedure.

The law-of-reflection practical explains the full marking method. Angles are measured from the normal at the point of incidence, not from the mirror surface.

Check the power supply and allow for lamp heat

Use only the specified compatible supply and prepared leads. Route cables so moving paper or a measuring tool cannot drag the source or holder. Do not improvise a connection or assume a low-voltage label means every part of the setup is safe.