Reflection and Mirrors

This section delves into the principles of reflection and how light interacts with mirrors and other reflective surfaces.

Reflection occurs when light bounces off a surface. The behavior of reflected light follows specific rules:

1. The angle of incidence is equal to the angle of reflection.
2. The incident ray, reflected ray, and normal all lie in the same plane.

Vocabulary: The angle of incidence is the angle between the incoming light ray and the normal, while the angle of reflection is the angle between the reflected ray and the normal.

Types of reflection:

1. Specular reflection: Occurs on smooth, shiny surfaces like mirrors, producing clear images
2. Diffuse reflection: Happens on rough, uneven surfaces, scattering light in various directions

Example: A plane (flat) mirror produces a laterally inverted image, where left becomes right and vice versa. This is because your brain assumes light travels in straight lines and interprets the reflected light as coming from behind the mirror.

Ray diagrams are used to illustrate the path of light during reflection:

• Incident ray: The incoming light ray
• Point of incidence: Where the light ray hits the surface
• Normal: The perpendicular line at the point of incidence
• Reflected ray: The light ray bouncing off the surface

Highlight: In a plane mirror, parallel rays are reflected as parallel rays, producing a clear image. On rough surfaces, light rays are reflected in different directions, resulting in diffuse reflection.

Light and Its Properties

Light is a form of energy that travels in straight lines through waves. This section explores the nature of light and its basic properties.

• Light sources are objects that emit light, such as the sun or a lamp.
• Light travels in straight lines in all directions from its source.
• Waves can be categorized into two types:
  1. Longitudinal waves (e.g., sound) that transfer energy through particles
  2. Transverse waves or electromagnetic waves (e.g., light, infrared, gamma) that don't require particles to travel

Vocabulary: Luminous objects give off light, while non-luminous objects only reflect light from other sources.

When light interacts with objects, it can:

1. Be transmitted (pass through)
2. Be reflected (bounce back)
3. Be absorbed (stay inside the object)

Example: When reading a book under a lamp, light from the lamp hits the book, reflects off the page, and enters your eye. Some light also reaches your eye directly from the lamp.

Objects can be classified based on how they interact with light:

• Transparent: Allow light to pass through clearly (e.g., clear glass window)
• Translucent: Let light through but scatter it, making objects appear blurry
• Opaque: Do not allow light to pass through

Highlight: White and pale objects reflect most of the light shining on them, while darker objects absorb more light.

Shadows are formed when an opaque object blocks the path of light:

• A small light source produces a sharp shadow called an umbra
• A large light source creates a fuzzy-edged shadow known as a penumbra

Definition: The normal is an imaginary line drawn perpendicular to the surface at the point where a light ray hits it.