## How does density affect light refraction?

The angle and wavelength at which the light enters a substance and the density of that substance determine how much the light is refracted. When light passes from a more dense to a less dense substance, (for example passing from water into air), the light is refracted (or bent) away from the normal.

## What is refraction and how does it change light waves as they pass through different media?

Refraction is an effect that occurs when a light wave, incident at an angle away from the normal, passes a boundary from one medium into another in which there is a change in velocity of the light. The wavelength decreases as the light enters the medium and the light wave changes direction.

## What is the bending of light as it passes through different media?

Refraction is the bending of light (it also happens with sound, water and other waves) as it passes from one transparent substance into another. This bending by refraction makes it possible for us to have lenses, magnifying glasses, prisms and rainbows.

## Why does a ray of light bend when it travels from one medium into another medium?

A ray of light bends while going from one medium to another because of the phenomena of refraction. When the ray of light travels from one medium to another as the velocity of the light ray will either increase or decrease depending on the optical density of the material.

## How does a light ray bend when it travels from denser to rarer medium?

When light travels from a denser medium to a rarer medium, it bends away from the normal, as illustrated to the left. This behavior follows from Snell’s Law. As you saw before, the larger angle must be in the medium having the lower index of refraction. On the previous pages, that was medium 1, but here it is medium 2.

## Does the value of speed of light change with medium?

Yes. Light is slowed down in transparent media such as air, water and glass. The ratio by which it is slowed is called the refractive index of the medium and is always greater than one. When people talk about “the speed of light” in a general context, they usually mean the speed of light in a vacuum.

Albert Einstein

## Does light travel faster in air or water?

Explain that unlike sound, light waves travel fastest through a vacuum and air, and slower through other materials such as glass or water.

## In what path does light travel?

Whether it is traveling through air, water, glass, diamond, a smoky Broadway stage, or any other transparent substance (or in nothing — the vacuum of space), light travels in a straight path until it encounters a different medium. So straight that analogies fail — the path of light is the Ultimate Straight Line.

## What if light had mass?

The speed of light is special: nothing with mass can move at that speed, or accelerate to it. If photons have mass, then obviously the “speed of light” becomes a misnomer. Massless particles would still travel at that speed — if any particles end up being massless after the carnage is done.

## Why does light have energy but no mass?

Since photons (particles of light) have no mass, they must obey E = pc and therefore get all of their energy from their momentum. But an object with zero energy and zero mass is nothing at all. Therefore, if an object with no mass is to physically exist, it can never be at rest. Such is the case with light.

## Does Light Have matter?

Light is not matter. Light is made up of “things” called photons, and these photons can possess some of the properties of matter. For example, they are always moving, and when they move, they can exert a (usually very small) force on an object (just like moving matter can). But most of the time, light is just light.

## What gives matter mass?

The Higgs field gives mass to fundamental particles—the electrons, quarks and other building blocks that cannot be broken into smaller parts. The energy of this interaction between quarks and gluons is what gives protons and neutrons their mass. Keep in mind Einstein’s famous E=mc2, which equates energy and mass.