Refraction of Light — Interactive Diagram
See why a straw looks bent in water — light changes direction when it passes between air and glass or water.
TL;DR: See why a straw looks bent in water — light changes direction when it passes between air and glass or water.
Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated
Refraction of Light: See why a straw looks bent in water — light changes direction when it passes between air and glass or water.
Why it matters: Refraction explains lenses, the human eye, mirages and why pools look shallow — a core optics concept with many numericals.
Refraction of Light — Step by Step
- Light travels in a straight line through air. When it hits a denser medium (glass) at an angle, it BENDS.
- Entering the glass, light bends TOWARDS the normal (slows down). Leaving it, light bends AWAY from the normal (speeds up).
- The ray comes out parallel to how it went in, just shifted sideways. This bending is why a straw in water looks broken!
Quick Notes — the Exam Crux
- Refraction is the bending of light as it passes from one transparent medium into another.
- It happens because light changes speed between media (it travels slower in a denser medium).
- Going into a denser medium (air → glass/water): light bends toward the normal.
- Going into a rarer medium (water → air): light bends away from the normal.
- The amount of bending depends on the refractive index of the medium.
- Refraction explains lenses, the working of the eye, mirages, and why a pool looks shallower than it is.
Remember It (Memory Trick)
Light bends when it changes medium. Into a denser medium (air→water) it bends TOWARD the normal; into a rarer medium it bends AWAY. "Denser = slower = bends toward."
Real-Life Example
A straw in a glass of water looks bent or broken at the surface — light from the straw bends as it leaves the water, fooling your eyes about where the straw really is.
Test Yourself
Why does light bend when it enters water from air?
Light slows down in the denser water, which changes its direction — it bends toward the normal.
A ray passes from glass into air — does it bend toward or away from the normal?
Away from the normal, because it is entering a rarer medium.
Give one everyday example of refraction.
A straw looking bent in a glass of water (or a pool appearing shallower than it really is).
📖 Read the full explanation of Refraction of Light →
More Visual Lessons
- A Simple Electric Circuit
- Dispersion of Light (Prism)
- How We Hear (Sound)
- Electromagnetic Induction
- Series vs Parallel Circuits
- Magnetic Field of a Bar Magnet
🤖 Stuck on any of these? Ask Syllab's free AI Tutor to explain step by step →