Reflection and Mirrors

Nature of Light

• Light as a Particle: Proposed by Newton (1665) as streams of particles called corpuscles.

• Light as a Wave: Proposed by Maxwell (1873) and Hertz (1887) with the existence of electromagnetic waves.

Reflection of Light

• Definition: The process of light bouncing off surfaces, exemplified in plane mirrors.

Laws of Reflection (Page 3)

• Angle of Incidence (𝜽i): Angle between the incident ray and the normal.

• Angle of Reflection (𝜽r): Angle between the reflected ray and the normal.

• Law Statement: 𝜽i = 𝜽r.

• Understanding Rays:

  • Normal Line: Imaginary line perpendicular to the mirror surface.

  • Incident Ray: Light ray approaching the mirror.

  • Reflected Ray: Light ray leaving the mirror.

Properties of Images in Plane Mirrors (Page 4)

• Characteristics of Images:

  • Appear behind the mirror (virtual image).

  • Height of image (h') is equal to the height of the object (h): h' = h.

  • Magnification (M):

    • M > 1: image larger than the object.

    • M < 1: image smaller than the object.

    • +M: image is upright.

    • -M: image is inverted.

Types of Mirrors (Concave and Convex) (Page 5)

• Concave Mirror (Converging):

  • Properties: Bulges away from the light source, parallel incident rays converge.

  • Image: Can be magnified.

• Convex Mirror (Diverging):

  • Properties: Bulges towards the light source, parallel incident rays diverge after reflection.

  • Image: Reduced in size.

Key Concepts of Curved Mirrors (Page 6)

• Important Points:

  • Center of Curvature (C): Center of the sphere from which the mirror is a part; distance known as radius.

  • Vertex (V): Center of the mirror.

  • Focal Point (F) and Focal Length (f): Point between center of curvature and vertex.

  • Principal Axis (P): Horizontal line.

Principal Rays in Curved Mirrors (Page 6)

1. P-F Ray: Ray travels parallel to the principal axis and passes through the focal point.

2. F-P Ray: Ray passes through the focal point and reflects parallel to the principal axis.

3. C-C Ray: Ray travels through the center of curvature and reflects back on itself.

4. V Ray: Ray reflecting off the vertex.

Characteristics of Images Produced by Concave Mirrors (Page 7)

• Image Characteristics:

  • Virtual and upright for objects between the mirror and the focal point.

  • Real and inverted for objects beyond the focal point.

• The magnification and orientation can change based on the positioning of the object.

Characteristics of Images Produced by Convex Mirrors (Page 8)

• Erect Image: Image formed is always virtual and smaller than the object when the object is placed greater than the focal length.

Mirror Equation and Sign Conventions (Page 9)

• Example: A concave spherical mirror has a focal length of 12 cm; an object placed 6 cm in front results in specific magnification and orientation outcomes depending on calculations using the mirror equation.

Position of the Image in Convex Mirrors (Page 10)

• Example Question: A convex mirror with a focal length of 12 cm and an object placed 6 cm in front results in determining the position of the image behind the mirror.