8th Grade Reflection , Refraction and Dispersion of light
How Light Changes Direction
Light travels fast almost 300,000 kilometers per second in a vacuum. But what happens when it hits a surface or moves from one material to another, like from air into water? It can either bounce back or bend. These two effects are known as reflection and refraction.
🔁 What Is Reflection?
Reflection happens when light bounces off a surface. You see your face in a mirror because light rays hit the smooth surface and bounce back in the same pattern. This makes your reflection appear almost identical to you.
📏 The Laws of Reflection:
The angle of incidence equals the angle of reflection.
That means the angle the light hits the surface is the same as the angle it bounces off.
The incident ray, reflected ray, and the normal line all lie in the same plane.
The “normal” is an imaginary line perpendicular to the surface at the point where light hits.
✨ Fun Fact: Smooth surfaces like mirrors create regular reflection, while rough surfaces like paper scatter light in many directions called diffuse reflection.
🔀 What Is Refraction?
Refraction happens when light bends as it passes from one material to another. This bending occurs because light changes speed depending on the medium it travels through.
👓 Example: Why a Straw Looks Bent in Water
When you place a straw in a glass of water, it looks like it’s broken or bent. That’s because light slows down when it moves from air (less dense) into water (more dense), causing it to change direction.
According to The Physics Classroom:
Light travels fastest in a vacuum, slower in air, and even slower in water or glass.
The greater the change in speed, the more the light bends.
Our brain assumes light travels in a straight line, so it misinterprets the bent light path causing optical illusions.
🧠 Why Does It Matter?
Understanding how light behaves helps us in daily life:
Reflection lets us see ourselves in mirrors, design better lighting, and build laser tools.
Refraction allows for the creation of eyeglasses, microscopes, cameras, and even fiber-optic internet cables.
🧪 Try It Yourself!
Reflection Activity
Shine a flashlight at a small mirror on a desk. Measure the angle at which the light hits and the angle it reflects. They should be the same!
Refraction Activity
Put a pencil in a clear glass of water. Look at it from the side. Notice how it appears bent? That’s refraction in action!
