Video Lecture 1: The Geometry of Rays — Laws of Reflection, Plane Mirrors and Lateral Inversion

# Video Lecture 1: The Geometry of Rays — Laws of Reflection, Plane Mirrors and Lateral Inversion
**Instructor:** Dr. Ananya Sharma | **Duration:** ~05:50 mins

### Introduction: What Makes Things Visible?
Eyes alone cannot see an object! We see an object only when light emitted by it or reflected from its surface enters our eyes.
When a beam of light strikes a smooth, polished boundary—like a silvered glass mirror—it bounces back into the same medium. This phenomenon is called the **reflection of light**.

### Fundamental Laws of Reflection
Let us define our optical terms at the boundary:
- **Incident Ray:** The incoming light ray falling upon the reflecting surface.
- **Point of Incidence ($O$):** The point where the incident ray strikes the mirror.
- **Normal ($N$):** An imaginary perpendicular line drawn to the surface at the point of incidence.
- **Reflected Ray:** The light ray bounced back from the reflecting surface.
- **Angle of Incidence ($\angle i$):** The angle between the incident ray and the normal.
- **Angle of Reflection ($\angle r$):** The angle between the reflected ray and the normal.

**The Two Fundamental Laws of Reflection:**
1. **First Law:** The angle of incidence is always equal to the angle of reflection:
$$\angle i = \angle r$$
2. **Second Law:** The incident ray, the normal at the point of incidence, and the reflected ray all lie in the **same plane**.

### Image Characteristics in a Plane Mirror:
1. The image is **virtual** (cannot be captured on a physical screen).
2. The image is **erect** (upright).
3. The image is of the **same size** as the object.
4. The image distance behind the mirror equals the object distance in front of it.
5. **Lateral Inversion:** The left side of the object appears on the right side of the image, and vice versa (which is why "AMBULANCE" is written in reverse on emergency vehicles).