# What is the actual cause of refraction?

• jeebs
In summary, the ray will be refracted when it enters the material. The explanation of this depends on the dielectric constant of the material.
jeebs
Pretty straightforward question I hope. When the ray crosses into the material it will be refracted (ie. it's path changes direction). What is the explanation of this? All I have really been taught so far is that it does. I gather that it depends on the dielectric constant of a material but I know nothing more than that at this stage. Can anyone enlighten me?

How far down the rabbit hole are we going?

Short answer: refraction is caused by the response of the material to the impinging EM wave.

As an EM wave enters a material, it interacts with it. The electrical part re-orients the electrical dipoles and the magnetic part re-orients the magnetic dipoles. The material re-orients, stretches, or whatever it does in response, adding it's own polarity to the wave, enhancing it, but slowing it and diminishing it as the material response time becomes a factor. We boil all these effects into the complex numbers of permittivity (loosely known as the dielectric constant, strictly, the dielectric constant is the real part of permittivity) and permeability.

Separately, scientists have observed the familiar "light bending" phenomenon, and developed an empirical shorthand called "index of refraction" that was just a geometric ratio. However, the linkage between this simple geometric coefficient and the underlying physics above turns out to be marvelously elegant.

The refractive index is the square root of the product of permittivity of and permittivity. At optical frequencies (*cough* wavelengths, sorry, sounded like an EE there) the relative permeability is nearly always 1, and in clearish materials, the imaginary part of the permittivity is very very small, so the index refraction is usually just the square root of the dielectric constant.

Cool, eh?

thanks man, I'm staring down that rabbit hole now (just started an "optical properties of solids" module). hopefully this will mean a lot more to me in a few months.

## What is the actual cause of refraction?

The actual cause of refraction is the change in speed and direction of light as it passes through different mediums. When light travels from one medium to another with a different density, its speed changes and causes the light to bend or refract.

## How does refraction occur?

Refraction occurs when light passes through a medium with a different density, such as air to water or air to glass. As the light enters the new medium, it changes speed and direction, causing it to bend.

## Why does refraction happen?

Refraction happens because different mediums have different densities, which affects the speed of light. When light travels from one medium to another, it changes speed and direction, resulting in refraction.

## What factors affect refraction?

The main factors that affect refraction are the change in density between two mediums and the angle at which the light enters the second medium. The greater the difference in density and the steeper the angle of incidence, the more the light will refract.

## How is refraction used in daily life?

Refraction has many practical applications in daily life. It is used in the design of lenses for eyeglasses and cameras, as well as in the formation of rainbows and other optical illusions. It is also used in the field of medicine for procedures like LASIK eye surgery.

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