Topic 7: One-Page Revision Sheet

Chapter 12: Optics – One Page Revision

1. Optics

Branch of physics dealing with the study of light and its behaviour such as reflection and image formation.

2. Reflection of Light

Reflection is the phenomenon in which light returns to the same medium after striking a surface.

Laws of Reflection

• Incident ray, reflected ray and normal lie in the same plane
• Angle of incidence = Angle of reflection (∠i = ∠r)

3. Plane Mirror

• Forms virtual and erect image
• Image is same size as object
• Image distance = object distance
• Shows lateral inversion

4. Spherical Mirrors

Mirrors whose reflecting surface is part of a sphere.

Types

• Concave mirror – converging
• Convex mirror – diverging

Important Terms

• Pole (P)
• Centre of curvature (C)
• Radius of curvature (R)
• Focus (F)
• Focal length (f)

Important Relations

f = R / 2

5. Mirror Formula

1/f = 1/v + 1/u

6. Magnification

m = −v / u

7. Concave Mirror – Image Formation

• Can form real or virtual images
• Real images are inverted
• Virtual image formed when object is between F and P

8. Convex Mirror – Image Formation

• Always forms virtual, erect and diminished images
• Image formed behind mirror between P and F

9. Uses

• Concave mirror: shaving mirror, headlights
• Convex mirror: rear-view mirror

10. Important CET Points

• Laws of reflection
• Characteristics of images by plane mirror
• Mirror formula & magnification numericals
• Image nature for different object positions
• Concave vs convex mirror comparison