Reflection of light (including specular and diffuse) | Exit Quiz | Oak National Academy

Match each word with its definition.

• wavefront

• an imaginary line drawn at 90° to a surface

• ray

• a straight line drawn to show the direction a wave travels

• normal

• a line drawn to represent where the peak of a wave is

Answer explanation

Rays are drawn to show the direction in which waves travel. Wavefronts are drawn perpendicular to rays, and represent the peaks of the wave. The angles of rays are measured to the normal line.

A person speaks to another person across a room. Which statements are correct?

• Speaking makes air molecules oscillate.

• Speaking makes energy travel from the speaker to the listener.

• Speaking makes air molecules travel from the speaker to the listener.

Answer explanation

A wave occurs when parts of a medium oscillate (move back and forth repeatedly). As the sound wave travels, air molecules oscillate. The wave carries energy, but not air, to the listener. (If air moved away from the speaker, they could not breathe!)

This diagram shows rays reflecting from a rough surface. This type of reflection is called ___ reflection.

Answer explanation

Diffuse reflection is reflection in many directions from a rough surface such as a brick or wall painted with matte paint. In this representation, each ray still obeys the law of reflection but each part of the surface is at a different angle.

Which statement describes the law of reflection?

• The incident ray equals the reflected ray.

• The angle of incidence equals the angle of reflection.

• The incident ray is perpendicular to the reflected ray.

• The angle of incidence and the angle of reflection add to 90°.

Answer explanation

The law of reflection states that the angle of incidence and the angle of reflection are equal.

Here is a ray diagram for the reflection of a wave. In which diagram is the angle of reflection shaded?

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Answer explanation

The angle of reflection is the angle between the reflected ray and the normal line (perpendicular to the mirror).

The ray diagram represents the reflection of a light wave by a mirror. Which diagram correctly shows the wavefronts?

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Answer explanation

The wavefronts are perpendicular (at right angles) to the ray.