Reflection

Light waves reflect from surfaces. When waves reflect, they obey the law of reflection: the angle of incidence equals the angle of reflection.

• The normal is a line drawn at right angles to the reflector.
• The angle of incidence is between the incident (incoming) ray and the normal.
• The angle of reflection is between the reflected ray and the normal.

Smooth surfaces produce strong echoes when sound waves hit them, and they can act as mirrors when light waves hit them. The waves are reflected uniformly and light can form images. In the plane (flat) mirror, the image appears to be behind the mirror.

Constructing a ray diagram

In a ray diagram, the mirror is drawn a straight line with thick hatchings to show which side has the reflective coating. The light rays are drawn as solid straight lines, each with an arrowhead to show the direction of travel.

Make sure that the rays obey the law of reflection.

a ray diagram

Diffraction

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