Optical ray diagrams need to be drawn very carefully and with precision as they need to 'look right' and you may have to measure the angles on your diagram.

You should use a SHARP pencil and a ruler to construct these diagrams. You may need a protractor and a rubber.

Label diagrams in ink.

A boundary is drawn between media of different optical density (air/glass, air/water etc.)

In a diagram a boundary is represented by a solid line, drawn with a ruler and sharp pencil.

A boundary is shaded at the back with chevrons if it is reflective (i.e. if light rays will reflect off it)

A ray is also represented by a solid line. It always has an arrow on it to show which way it is going.

A normal is the line you draw perpendicular to the boundary (at right angles to it). It is drawn so that you can measure angles from it. This is sometimes drawn as a solid line with a 'right angle symbol' put between it and the boundary OR as a dashed line - again the symbol showing it is perpendicular to the bounday must be included.

Angles are always measured from the normal to the ray.

Click here to go to the page on how to construct rays through lenses

LOJ October 2002