Draw a labelled ray diagram to show the refraction of light through a triangular glass prism. Mark the angle of incidence, angle of refraction, angle of emergence and angle of deviation.

1. 1 · Open in one line. A prism refracts light at two inclined faces, so the emergent ray is deviated towards its base.
2. 2 · Draw the diagram. [Diagram: prism ABC; incident ray to E on AB; dotted normals at E and F; ray EF inside bent towards the normal; emergent ray from F bent away from the normal; dotted extensions meet; ∠i, ∠r, ∠e, ∠D and ∠A marked]
3. 3 · Describe the two bendings. At E (air to glass) the ray bends towards the normal. At F (glass to air) it bends away from the normal.
4. 4 · Name the deviation. The angle between the extended incident ray and the emergent ray is the angle of deviation D.
5. 5 · Daily-life link. Cut-glass chandeliers sparkle because each piece bends light like a small prism.
6. 6 · Close in one line. So a prism deviates light towards its base.

Scoring tip: Use dotted lines for the normals and for the extended rays that make ∠D. Write each angle label inside its angle.