๐ฆ Chapter 10 – Light: Mirrors and Lenses
๐ Introduction
- ๐ช Plane mirrors → form erect & same-size images
- ๐ Curved mirrors → form different images:
- Enlarged
- Diminished
- Inverted
- Erect
๐ These curved mirrors are called:
Spherical Mirrors
๐ช 10.1 What Are Spherical Mirrors?
๐ Definition:
Mirrors whose reflecting surface is part of a sphere
๐ Types of Spherical Mirrors
๐น 1. Concave Mirror
- Reflecting surface curves inward
๐ธ 2. Convex Mirror
- Reflecting surface curves outward
๐ฅ Example:
- A shiny spoon acts like a spherical mirror
๐ Inner side → concave
๐ Outer side → convex
⚙️ How Mirrors Are Made
- Glass is curved and polished
- Coating decides type:
Coating Position | Mirror Type |
Outer surface | Concave |
Inner surface | Convex |
๐ 10.2 Image Formation by Mirrors
๐ช 1. Concave Mirror
๐ Characteristics:
- Object near → image erect & enlarged
- Object far → image inverted
๐ Image Nature:
- Can be:
- Erect
- Inverted
- Enlarged
- Diminished
๐ Depends on object distance
๐ 2. Convex Mirror
๐ Characteristics:
- Image is always:
- Erect
- Diminished (smaller)
๐ Distance Effect:
- Image becomes slightly smaller as object moves away
๐ช 3. Plane Mirror
๐ Characteristics:
- Image is:
- Erect
- Same size
๐ Special Property:
- Lateral inversion (left-right reversal)
๐ ️ Uses of Mirrors
๐ฆ Concave Mirrors
- Torch reflectors ๐ฆ
- Car headlights ๐
- Dentist mirror ๐ฆท
- Telescopes ๐ญ
๐ Convex Mirrors
- Side-view mirrors
- Road safety mirrors
- Security mirrors in shops
๐ Provide wide field of view
๐ 10.3 Laws of Reflection
๐ Important Terms:
- Incident Ray → incoming light
- Reflected Ray → outgoing light
- Normal → perpendicular line
๐ Angles:
- Angle of incidence (i)
- Angle of reflection (r)
⭐ Laws of Reflection:
1.
Angle of incidence = Angle of reflection
2.
Incident ray, reflected ray, and normal lie in same plane
๐ Reflection in Different Mirrors
- Plane mirror → parallel rays remain parallel
- Concave mirror → rays converge
- Convex mirror → rays diverge
๐ฅ 10.3.1 Concentration of Light
๐ Concave Mirror:
- Can focus sunlight to a point
๐ Heat increases → can burn paper
⚙️ Applications:
- Solar cookers ๐ณ
- Solar furnaces
- Power generation
๐ 10.4 What Is a Lens?
๐ Definition:
Lens = Transparent object that allows light to pass through
๐ Types of Lenses
๐น 1. Convex Lens
- Thicker in middle
- Converges light
๐ธ 2. Concave Lens
- Thinner in middle
- Diverges light
⚠️ Difference from Mirror:
- Mirrors → reflect light
- Lenses → allow light to pass
๐ 10.5 Image Formation by Lenses
๐ 1. Convex Lens
๐ Characteristics:
- Object near → erect & enlarged
- Object far → inverted
๐ Image can be:
- Enlarged
- Diminished
- Erect
- Inverted
๐ 2. Concave Lens
๐ Characteristics:
- Image always:
- Erect
- Diminished
๐ 10.6 Convergence and Divergence
๐น Convex Lens:
Converging Lens
๐ธ Concave Lens:
Diverging Lens
๐ฅ Important:
- Convex lens can also burn paper by focusing sunlight
๐ฏ 10.7 Uses of Lenses
๐ Daily Life:
- Eyeglasses
๐ฌ Instruments:
- Microscopes
- Telescopes
- Cameras ๐ธ
๐️ Human Eye:
- Contains convex lens
- Changes shape to focus
๐ Snapshots (Quick Revision)
⚡ One-Line Points
- Concave mirror:
- Forms all types of images
- Convex mirror:
- Always erect & diminished
- Laws of reflection:
- i = r
- Rays lie in same plane
- Concave mirror → converges light
- Convex mirror → diverges light
- Convex lens:
- Converges light
- Forms different types of images
- Concave lens:
- Always erect & diminished
- Diverges light
๐ฏ Final Conclusion
Light behaves differently depending on:
๐ Mirror shape + Lens type
๐ Final Formula:
Reflection + Refraction = Image Formation
๐ง Learning Outcome:
- Understand mirrors & lenses
- Identify image types
- Apply concepts in real life
