* Refractive Index: Glass has a higher refractive index than air. The refractive index is a measure of how much a material slows down light.

* Speed of Light: The speed of light is constant in a vacuum, but it slows down when it travels through a medium like air or glass. The higher the refractive index, the slower the light travels.

In simpler terms: Imagine light as a car traveling on different roads. Air is like a smooth highway, allowing the car (light) to travel fast. Glass is like a bumpy, crowded road, making the car (light) travel slower.

Key Points:

* Frequency Remains Constant: While the velocity of light changes, its frequency remains constant when it enters a different medium.

* Wavelength Changes: The wavelength of light decreases when it enters glass, because the speed of light is lower in glass.

* Bending of Light: The change in velocity also causes the light ray to bend, a phenomenon known as refraction.

Let me know if you'd like more details on refraction!