Introduction
Have you ever stood in front of a mirror and seen your exact image looking back at you? Or dropped a spoon into a glass of water and noticed it looked bent? These are not magic tricks—they are clear examples of how light behaves.
Light does two main things when it hits a surface or passes into another material:
- It bounces back: this is called reflection
- It bends: this is called refraction
These two behaviors are everywhere—mirrors, glasses, lenses, rainbows, and even in how your eyes see. In this lesson, we’ll break down reflection and refraction using real-life examples, easy language, and simple diagrams to help you truly understand.
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What Is Reflection of Light?
Reflection happens when light hits a surface and bounces back into the same medium.
The most common example is when you see your image in a mirror.
There Are Two Main Types of Reflection:
1. Regular Reflection (also called Specular Reflection)
- Happens on smooth and shiny surfaces like mirrors or calm water.
- Produces clear images.
2. Diffuse Reflection
- Happens on rough or uneven surfaces like walls, wood, or paper.
- Light rays scatter in many directions.
- No clear image is formed.
Laws of Reflection
There are two important rules that light always follows when it reflects:
- The angle of incidence is equal to the angle of reflection.
(Angle in = Angle out) - The incident ray, the reflected ray, and the normal all lie on the same plane.
What is a Normal?
The normal is an imaginary line drawn at 90° (perpendicular) to the surface where light hits.
What Is Refraction of Light?
Refraction is the bending of light when it passes from one medium into another. For example, from air into water, or from glass into air.
Why does it bend? Because light changes speed in different materials.
- It slows down in denser materials like glass or water.
- It speeds up in less dense materials like air.
This bending causes effects like a pencil appearing bent in water or objects looking closer in a swimming pool.
Laws of Refraction
Like reflection, refraction also follows two laws:
- The incident ray, refracted ray, and normal all lie on the same plane.
Snell’s Law:
This law gives the relationship between the angles and the medium:
n₁ sin i = n₂ sin r
Where:
- i is the angle of incidence
- r is the angle of refraction
- n is the refractive index, which tells how much light slows down in that medium
Refractive Index
The refractive index shows how much light bends when entering a medium. A higher refractive index means more bending.
Formula:
Refractive Index (n) = Speed of light in vacuum / Speed of light in the medium
Reflection vs Refraction: What’s the Difference?
| Feature | Reflection | Refraction |
| What happens? | Light bounces back | Light bends when changing medium |
| Medium | Same medium | Goes from one medium to another |
| Speed of light | Doesn’t change | Changes (increases or decreases) |
| Example | Seeing yourself in a mirror | Pencil appearing bent in water |
| Image Formed | Same size, flipped | May be larger or smaller |
Core Concepts Table
| Term | Meaning |
| Incident Ray | Incoming light ray that hits a surface |
| Reflected Ray | Light ray that bounces back |
| Refracted Ray | Light ray that bends in a new medium |
| Normal | Line at 90° to the surface at the point of contact |
| Angle of Incidence | Angle between incident ray and normal |
| Angle of Refraction | Angle between refracted ray and normal |
Real-Life Applications of Reflection and Refraction
Reflection:
- Mirrors in bathrooms and vehicles
- Solar cookers use reflective surfaces to focus sunlight
- Periscopes in submarines
Refraction:
- Lenses in eyeglasses and cameras
- Magnifying glasses to zoom in on objects
- Rainbows caused by refraction, reflection, and dispersion in raindrops
- Optical fibers for internet data transmission using total internal reflection
Frequently Asked Questions
Q1. Why does a pencil look bent in water?
Because light bends when it passes from water to air—this is refraction.
Q2. Can reflection happen on rough surfaces?
Yes, but it becomes diffused reflection—light is scattered and no clear image forms.
Q3. What is the angle of incidence?
It’s the angle between the incident ray and the normal.
Q4. Is the refractive index a unit?
No, it’s a ratio and has no units.
Q5. Why do we see rainbows?
Because of refraction, reflection, and dispersion of light inside raindrops.
Fun Facts
- Light travels fastest in vacuum (3 × 10⁸ m/s) and slowest in glass.
- Some animals (like cats and deer) have eyes that reflect light at night—this is called retro-reflection.
- Fibre optic cables use total internal reflection to carry internet signals over long distances.
- A plane mirror flips your image left to right but not top to bottom!
Conclusion
Reflection and refraction are two amazing ways that light behaves when it meets a surface or passes from one material to another. They help us see, read, focus, and even connect to the internet.
From mirrors in your room to the lenses in your eyes, from rainbows in the sky to headlights on a road—the science of light is everywhere.
By understanding how light bounces (reflection) and bends (refraction), you’ll start seeing these fascinating effects all around you—right from your home to the vastness of space.
