# A few really quick questions about light from a physics noob.

• PeteGerasia
In summary, the frequency of light can be changed by changing the medium it passes through or using the doppler effect. Lasers are created by pumping energy into a special medium, causing an avalanche of photons to be released in a coherent beam. The frequency of light can also be changed by using gravitational red shift or fluorescent material.
PeteGerasia
I have no idea about physics relating to light. I have just a couple questions for you guys.

First, what can be done to change the wavelength of light from the visible spectrum to the IR spectrum? And how does it actually work?

Second, how exactly are lasers created and what determines the intensity.

I'm not really looking for a super high tech definition. Just a very basic explanation. And maybe some good links that could provide further reading.

Thanks for any responses.

Changing the frequency can be done by changing the medium the light is passing through or by the doppler effect in extremely large distances.

As for the lasers, this is taken from Dr. Michio Kaku's book Physics of the Impossible:
In a laser you first begin with a special medium that will transmit
the laser beam, such as a special gas, crystal, or diode. Then you pump
energy into this medium from the outside, in the form of electricity, radio,
light, or a chemical reaction. This sudden influx of energy pumps
up the atoms of the medium, so the electrons absorb the energy and
then jump into the outer electron shells.
In this excited, pumped-up state, the medium is unstable. If one
then sends in a light beam through the medium, the photons will hit
each atom, causing it to suddenly decay down to a lower level, releasing
more photons in the process. This in turn triggers even more electrons
to release photons, eventually creating a cascade of collapsing
atoms, with trillions upon trillions of photons suddenly released into
the beam. The key is that for certain substances, when this avalanche
of photons is occurring all the photons are vibrating in unison, that is,
they are coherent.

Superstring said:
Changing the frequency can be done by changing the medium

As for the lasers, this is taken from Dr. Michio Kaku's book Physics of the Impossible:

The frequency stays the same when going from one medium to another ,
you can change the wavelength with gravitational red shift .
or by passing it trough a fluorescent material.

## 1. What is light?

Light is a form of electromagnetic radiation that is visible to the human eye. It is made up of particles called photons that travel in waves at a constant speed of approximately 299,792,458 meters per second.

## 2. How is light created?

Light is created when an object with thermal energy (such as the sun or a light bulb) emits photons. These photons then travel through space until they reach our eyes, allowing us to see the object or source of light.

## 3. What is the speed of light?

The speed of light, also known as the speed of electromagnetic radiation, is approximately 299,792,458 meters per second. It is considered to be the fastest possible speed in the universe.

## 4. What is the difference between white light and colored light?

White light is a combination of all the colors in the visible spectrum, while colored light is made up of specific wavelengths of light that correspond to a specific color. When white light is separated through a prism, it creates a rainbow of colors, each with their own unique wavelength.

## 5. How does light interact with matter?

Light can interact with matter in a few different ways. It can be absorbed, reflected, or transmitted. When light is absorbed, it is converted into another form of energy, such as heat. When it is reflected, it bounces off the surface of an object. When it is transmitted, it passes through an object, allowing us to see through it. The way light interacts with matter is dependent on factors such as the material of the object and the wavelength of the light.

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