IGCSE Physics 0625

3.2.1 Reflection of Light

This section introduces the fundamental concepts of light reflection, focusing on key terms like normal, angle of incidence, and angle of reflection. Understanding these concepts is crucial for analyzing various optical phenomena.

Key Terms

• Normal: A line drawn perpendicular to the surface at the point where the light ray strikes.
• Angle of Incidence (i): The angle between the incident ray and the normal.
• Angle of Reflection (r): The angle between the reflected ray and the normal.

Law of Reflection

The law of reflection states that the angle of incidence is equal to the angle of reflection.

Mathematically, this is expressed as:

$i = r$

Diagram

Explanation of Terms

Consider a light ray hitting a surface. The normal is a crucial reference line. The angle of incidence is how much the incoming light ray deviates from this normal. The angle of reflection is the same amount of deviation on the other side of the surface, as determined by the normal.

Table Summarizing Key Concepts

Term	Definition	Symbol
Normal	A line perpendicular to the surface at the point of incidence.	-
Angle of Incidence	The angle between the incident ray and the normal.	$i$
Angle of Reflection	The angle between the reflected ray and the normal.	$r$

Applications of the Law of Reflection

The law of reflection has numerous practical applications, including:

• Mirrors: Mirrors work based on the law of reflection.
• Optical Fibres: Optical fibres transmit light using total internal reflection, which is a consequence of reflection.
• Understanding optical phenomena like rainbows and refractions.