01
Theory and background
What is speed of light?
Light travels fastest in a vacuum and slows down in materials such as water or glass. The refractive index describes how much a medium reduces light speed.
PhysicsInteractive simulatorNo install
SpeedofLight
Explore how light travels and why its speed changes in different materials. Use the simulation to connect propagation speed with refractive index.
Light modelMedium, index, speed
Experiment guide
Use this simulator like a compact physics lab
Start with the concept, open the lab, then compare the observed motion with the key relationship. The sections below keep the theory, workflow, and common questions easy to scan.
SubjectPhysics
ModeInteractive
ModelLight model
AccessBrowser
02
How the simulation works
Interactive experiment flow
Launch the lab, adjust the available controls, and observe the result immediately. Use the simulation to connect the equation with what changes on screen.
Speed in a mediumv = c / n
Frequently asked questions
Speed of Light FAQ
01
What is the speed of light in vacuum?
The speed of light in vacuum is approximately 299,792,458 meters per second.
02
Does light slow down in glass?
Yes. Light travels slower in glass than in vacuum because glass has a refractive index greater than one.
03
What is refractive index?
Refractive index compares light speed in vacuum with light speed in a material.
04
Why does light bend?
Light bends when it changes speed while crossing between materials with different refractive indices.