Laser light What is a laser n Light

Laser light

What is a laser n Light Amplification by Stimulated Emission of Radiation. n A laser is a high intensity coherent monochromatic light wave that does not spread out over a large distance the way normal light sources do. n They come in all colors, however red is the most commonly one commercially sold as pointers.

Diagram These are coherent and monochromatic Laser Normal light These are incoherent These light waves are different colors. It looks white because it is a mixture of all colors

Coherent vs incoherent light n Coherent light is all photons have the same frequency (which is the color) all being in step with their wave pattern. n Incoherent light is many different frequencies with not pattern to their wave pattern.

Producing light n Light is produced by exciting an atom (adding energy) to a unstable or metastable state. n The energy is released by the atom as electromagnetic radiation (light) when it falls back to its ground state. n The difference between excited and ground state for any given atom is always the same so light comes out in little chunks or packets of energy called photons n Normally each atom releasing the energy has no relation to one another so the light is incoherent

Stimulated emission n In lasers, this process is put in sync. n The light released by one atom is absorbed by an identical atom already in an excited state. n This atom now releases 2 coherent light waves (in phase, same direction, same frequency). n This is repeated many times in a tube until the light waves find a way out.

Intensity and distance from the source. n Laser light doesn’t spread out (and lose its intensity) over a distance the way normal light does. n Therefore you can see the small dot after the light travels a large distance.

Uses n Medical science uses laser beams to burn away dangerous things (tumors, kidney stones) and the beam cauterizes the wound. n They are used for welding and cutting of metals. n The are used to measure n Optical storage of data (CD, DVD, Blu Ray) n And of course as pointers

Dangers n The warning label on lasers is not a joke. n The light is extremely intense and will damage the retina (back of the eye). n Just because someone doesn’t go blind instantly doesn’t mean they didn’t damage their sight.

-Polarizers and 3 -D effect

Polarization of light n Light travels in waves. n Some waves are oriented so their wave motion is traveling up and down, others are traveling side to side and every angle in between. n Light polarizers act like a picket fence in the way of the wave. n These can block out some waves.

A light wave

n There are several unpolarized incident beams of light. Only the vertical polarized beams make it through the first polarizer

If two polaroids are put at right angles to each other… n No light can get through. n These would block out all light. n The first one would only allow light with a certain polarization, the second would block that light out.

Where are these used n Certain low level reflections tend to come out polarized (all waves are up and down or side to side) n So polarizing lens are used to block out these reflections. n Cameras use them, and so do sunglasses (to block out sun glare at sunset or sunrise. n LCD (liquid crystal display) are also polarized, you can check if your sunglasses are polarizers by looking at a display and tilting your head.

3 -D movies also use light polarizers n Real. D 3 d uses light polarizers n There are two cameras projecting at a 3 -D movie theatre projecting almost identical images. n One camera has a polarizing filter up and down, the other is polarized side to side. n The glasses are light polarizers. One lens is up and down, the other is side to side. n Therefore one eye sees one image, the other eye sees a slightly different image.

3 -D effect n If each eye sees a slightly different image, you can create the illusion of depth. n The brain will interpret the two images as one.