Reflection of Light

Reflection of Light

Basic Principles

• Light travels in straight lines known as light rays.
• When light strikes an object, it is either absorbed, transmitted, or reflected.
• Reflection is when the light bounces back from a surface.
• Normal is an imaginary line at 90 degrees to the surface where the beam of light hits.
• Laws of reflection state that the angle of incidence is equal to the angle of reflection.

Types of Reflection

• Specular reflection occurs when light rays are reflected in a single direction by a smooth surface, such as a mirror.
• Diffuse reflection occurs when light rays are scattered in different directions by a rough surface.

Plane Mirrors

• Plane mirrors produce a virtual image that is laterally inverted (flipped horizontally).
• The image produced by a plane mirror is as far behind the mirror as the object is in front.

Properties of Images formed by Plane Mirror

• The image is the same size as the object.
• The image is as far behind the mirror as the object is in front.
• The image is virtual, which means it cannot be touched or projected onto a screen.
• The image is laterally inverted meaning left appears as right and vice versa.

Ray Diagrams

• Ray diagrams help us understand how light reflects off objects.
• For plane mirrors, two rays are commonly used: one parallel to the principal axis and one striking the centre of the mirror.
• The two reflected rays should meet at the same point behind the mirror, giving the position of the virtual image.

Uses of Mirrors

• Mirrors are used widely in optical instruments such as telescopes, cameras, and microscopes.
• Periscopes use two plane mirrors at 45-degree angles to allow the viewer to see over or around obstacles.
• Rear-view and side-view mirrors in vehicles are examples of the practical use of reflection in daily life.