Reflection is the return of a wave of energy, such as light, heat, sound, or radio, after it strikes a surface. Reflection can be compared to the action of a ball rebounding from a wall. A ball thrown at right angles to the wall will bounce back in the same line. If the ball is thrown along a path that makes less than a right angle with the wall, its path on rebounding will make the same angle with the wall, but on the opposite side of the point where the ball hit the wall. Imagine a line drawn to make a 90-degree angle with the wall at the point where the ball struck. The angle formed by the path of the thrown ball and this line is called the angle of incidence. The corresponding angle made by the rebounding ball is known as the angle of reflection. These two angles are equal.
The principle of reflection has many applications in daily living. The mirror (a glass coated with silver) reflects most of the light that strikes it. Polished surfaces, such as chromium, reflect most of the light that strikes them. Clear surfaces, such as window glass, reflect little light. The best example of the reflection of sound waves is the echo. Radar uses the reflection of radio waves.
