Need help on information on electromagnetic radiation especially in regards to lasers?
lasik eye surgery information
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snakesolid
Do all types of light travel the same speed on the spectrum. If so then how is it that some are more powerful than others? Does frequency and/or wavelength affect its power? How does light, specifically a laser emit heat energy? In regards to lasik eye surgery, how does the laser reconstruct the cornea but not affect the rest of the eye?
Answer
All electromagnetic waves, whether red, green or blue light, microwaves or radio waves have the same speed in vacuum. They have different speeds in different materials and that depends on the material and the wavelength of the light.
There are a number of reasons why the power of lasers is different. The first is due to Planck's law that says the energy of a photon is given by E = hc/lambda ... h is Planck's constant, c is the speed of light, and lambda is the wavelength. So photons of blue light (short wavelength) carry more energy than photons of red light (long wavelength). The other factor that governs the energy output of a laser is the number of photons produced.
The third thing is focusing - lasers are often characterised in terms of 'fluence' which is the amount of energy per unit area. A broad beam might have lots of energy but if it hits a material, that energy is distributed over a large area. A focused laser beam carries that energy to a smaller spot.
The fourth aspect is whether the laser is pulsed or not. A 1 Joule laser doesn't sound very impressive, but if it dumps that energy onto a material in a 1 nanosecond pulse, that works out to be 1 billion Watts of power since Power = Energy / Time.
Lasers can emit infrared radiation (such as a carbon dioxide laser) since infrared radiation (heat) is just a form of light. When a laser beam hits a material, the photons are absorbed by electrons and atoms which excites them. You can imagine atoms all jiggling about because of the energy from the laser light, and that means they have additional kinetic energy. Temperature is a measurement of the kinetic energy of atoms (or electrons). In other words, when a laser hits a material, it should get hot but the temperature depends on the pulse duration, the wavelength of light, and the material's chemical structure.
The reason a laser doesn't affect the rest of the eye is due to a property of materials called the 'skin depth' (nothing to do with human skin). This depends on the wavelength of light and the nature of the material (something called the dielectric constant). Basically, you choose the colour of laser so that it is absorbed in only the top layers of the material - the skin depth of metals, for example, to ultraviolet lasers is only about 10 nanometers! So the colour of the laser they use is only absorbed by the top layers of the cornea. Now, if the laser was continuous, then the absorbed energy would result in heat moving through the cornea. If you use a pulsed laser you heat up the top layers, but the heating is too short for it to have time to penetrate too far into the eye.
All electromagnetic waves, whether red, green or blue light, microwaves or radio waves have the same speed in vacuum. They have different speeds in different materials and that depends on the material and the wavelength of the light.
There are a number of reasons why the power of lasers is different. The first is due to Planck's law that says the energy of a photon is given by E = hc/lambda ... h is Planck's constant, c is the speed of light, and lambda is the wavelength. So photons of blue light (short wavelength) carry more energy than photons of red light (long wavelength). The other factor that governs the energy output of a laser is the number of photons produced.
The third thing is focusing - lasers are often characterised in terms of 'fluence' which is the amount of energy per unit area. A broad beam might have lots of energy but if it hits a material, that energy is distributed over a large area. A focused laser beam carries that energy to a smaller spot.
The fourth aspect is whether the laser is pulsed or not. A 1 Joule laser doesn't sound very impressive, but if it dumps that energy onto a material in a 1 nanosecond pulse, that works out to be 1 billion Watts of power since Power = Energy / Time.
Lasers can emit infrared radiation (such as a carbon dioxide laser) since infrared radiation (heat) is just a form of light. When a laser beam hits a material, the photons are absorbed by electrons and atoms which excites them. You can imagine atoms all jiggling about because of the energy from the laser light, and that means they have additional kinetic energy. Temperature is a measurement of the kinetic energy of atoms (or electrons). In other words, when a laser hits a material, it should get hot but the temperature depends on the pulse duration, the wavelength of light, and the material's chemical structure.
The reason a laser doesn't affect the rest of the eye is due to a property of materials called the 'skin depth' (nothing to do with human skin). This depends on the wavelength of light and the nature of the material (something called the dielectric constant). Basically, you choose the colour of laser so that it is absorbed in only the top layers of the material - the skin depth of metals, for example, to ultraviolet lasers is only about 10 nanometers! So the colour of the laser they use is only absorbed by the top layers of the cornea. Now, if the laser was continuous, then the absorbed energy would result in heat moving through the cornea. If you use a pulsed laser you heat up the top layers, but the heating is too short for it to have time to penetrate too far into the eye.
Can you have LASIK eye surgery and still be a Special Tactics Officer in the Air Force?
DA99O
I read up on requirements and it said No radial Keraotomy or something to that affect i looked up what that was and it is laser eye surgery. However I proceded to look up LASIK eye surgery which is now much more common and it is not The same as Radial Keraotomy (miss spelling, I know, sorry.) its a different kind of surgery so I don't no. Help please :)
Answer
Jeeper, your advice if someone took it could disqualify them for Air Force SOF service. You should do more research or cease answering questions like this if you aren't interested in providing accurate information.
LASIK will disqualify you for Military Free Fall. If you can't attend MFF, you can't be an STO, CRO, PJ or CCT. It's a requirement for all of those jobs.
PRK and LASEK are your only two options if you wish to serve in Air Force SOF.
We've had better results with PRK and the waiver process is getting faster. For those already on active duty, it's only a 6 month wait now. For those that have the surgery done as civilians, it is still 1 year but if someone really pushes for the waiver, it can be a bit less.
LASEK is a year regardless, active duty or civilian.
Go over to www.specialtactics.com. The policies are posted on the site, it's also the only source you should reference when seeking information about USAF Special Operations.
Jeeper, your advice if someone took it could disqualify them for Air Force SOF service. You should do more research or cease answering questions like this if you aren't interested in providing accurate information.
LASIK will disqualify you for Military Free Fall. If you can't attend MFF, you can't be an STO, CRO, PJ or CCT. It's a requirement for all of those jobs.
PRK and LASEK are your only two options if you wish to serve in Air Force SOF.
We've had better results with PRK and the waiver process is getting faster. For those already on active duty, it's only a 6 month wait now. For those that have the surgery done as civilians, it is still 1 year but if someone really pushes for the waiver, it can be a bit less.
LASEK is a year regardless, active duty or civilian.
Go over to www.specialtactics.com. The policies are posted on the site, it's also the only source you should reference when seeking information about USAF Special Operations.
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Title Post: Need help on information on electromagnetic radiation especially in regards to lasers?
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