Ok this left me scratching my head?

[Lasher]

After being here for a short while and reading a lot of post I thought I had started to get a handle on how lasers work and what the different terms here were referring to.

I was under the impression that the nm of a laser beam is the mesurment of the wavelength and told you what color the beam would be.

For instance all the green lasers I've been reading about are 532nm.

So in my head when I saw 532nm I think of it as a green laser.

Am I wrong about this? Does the nm not determine the color?

The reason I ask is I came accrost this purple.

200mW 532nm 1xTR18650 Purple Laser (L-200-p1) - Laser/Gun Accessories - Flashlights, Batteries and more - Quality China Goods

Please set me straight on this guys. I'm still trying to learn here

Thanks in advance

Lasher

 

[Prototype]

That's just a typo, and nm does indeed determine color. I wish I fully understood how lasers worked, but I don't feel like learning highly advanced physics

 

[Lasher]

LoL. Thanks Proto, I'm not wanting to learn that much either but that sure had me wondering if what I had already learned was totally wrong.

Safe bet that no one will be buying that one.

Lasher

 

[bobhaha]

actually wavelength is an exact measure of the colour of light (as well as its energy, velocity and other non related units). frequency of the light has nothing to do with the colour. Ok lets think of it this way, you are holding one end of a rope and the other end is fixed. If you make short fast waves the resulting wave will be of small wavelength (measured from peak to peak). now that corresponds to the colour of light. Now do the same thing but move the rope up and down slowly and move it up and down a long distance. This will result in a larger wavelenght (measured peak to peak).

Now if you do 1 short sharp wave thats a frequency of 1. you do it 4 times frequency of 4.. it has nothing to do with colour. (frequency is measured by how many waves pass through a certain point per second).

Also the smaller the wavelength the higher energy that wave possesses. eg gamma rays have incredably small wavelengths and high energy, where as ir has large wavelength and low energy.

heres a great picture explaining what i mean, short (high energy) wavelengths on left, long (low energy) wavelengths on the right.

The website has a typo as prototype said. That is a 405nm laser "violet" or "purple".

hope that helped -Adrian

 

[pullbangdead]

actually wavelength is an exact measure of the colour of light (as well as its energy, velocity and other non related units). frequency of the light has nothing to do with the colour. Ok lets think of it this way, you are holding one end of a rope and the other end is fixed. If you make short fast waves the resulting wave will be of small wavelength (measured from peak to peak). now that corresponds to the colour of light. Now do the same thing but move the rope up and down slowly and move it up and down a long distance. This will result in a larger wavelenght (measured peak to peak).

Now if you do 1 short sharp wave thats a frequency of 1. you do it 4 times frequency of 4.. it has nothing to do with colour. (frequency is measured by how many waves pass through a certain point per second).

Also the smaller the wavelength the higher energy that wave possesses. eg gamma rays have incredably small wavelengths and high energy, where as ir has large wavelength and low energy.

heres a great picture explaining what i mean, short (high energy) wavelengths on left, long (low energy) wavelengths on the right.

The website has a typo as prototype said. That is a 405nm laser "violet" or "purple".

hope that helped -Adrian

Actually, frequency and wavelength are both equally related to color, because the speed of light is fixed/constant. You have it backwards, speed has nothing to do with wavelength in vacuum, speed is the same for all wavelengths in vacuum. Frequency changes with wavelength. Since the waves are always moving the same speed, the wavelength and frequency are inextricably linked, both indicate color.

 

[Prototype]

The speed of light is 186,200 miles per second (random fact #1) and the light from the sun takes 542 seconds to get to Earth, so that'll give you an idea of how far it is from us to the big ball of fire. (random fact #2)

 

[scopeguy20]

Just a guess, but I think the new laser companies just copy stuff and make stupid mistakes as I have seen specs that were obviously wrong in a lot of web adds. -Glenn

 

[Crazy Jay]

I've got a smaller version of that pic. But just to let you guys know... I can see Radar with my own eyes
na I wish

Edit: That site offers "Quality China Goods" and "Quality Chinese Incorrect Listings"

 

[bobhaha]

Actually, frequency and wavelength are both equally related to color, because the speed of light is fixed/constant. You have it backwards, speed has nothing to do with wavelength in vacuum, speed is the same for all wavelengths in vacuum. Frequency changes with wavelength. Since the waves are always moving the same speed, the wavelength and frequency are inextricably linked, both indicate color.

Not exactly. A spectroscope is used to define light's wavelength. A spectroscope works by breaking light into the wavelengths (or spectra) that make it up. Some spectroscopes are made of diffraction grating- a material that has lots of little parallel lines that are approximately one wavelength apart. There may be 35,000 of these little lines in one inch of the material. When light hits the lines, it bends. Different wavelengths (colors) of light bend by different amounts, so it splits the light into its colors. Other spectroscopes are made of prisms- as light passes through the glass, the different wavelengths slow down by different amounts and are bent into their colors. Scientists can tell the elements present in a star by looking at its light through a spectroscope. Each element will have its own unique spectral lines of color, just as people each have a unique fingerprint..... meaning the only info you need to "find" the colour of light is the wavelength!

BTW source from wikipedia: Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths..... which is exactly what I said!

-Adrian

 

[pullbangdead]

actually wavelength is an exact measure of the colour of light (as well as its energy, velocity and other non related units). frequency of the light has nothing to do with the colour. Ok lets think of it this way, you are holding one end of a rope and the other end is fixed. If you make short fast waves the resulting wave will be of small wavelength (measured from peak to peak). now that corresponds to the colour of light. Now do the same thing but move the rope up and down slowly and move it up and down a long distance. This will result in a larger wavelenght (measured peak to peak).

Now if you do 1 short sharp wave thats a frequency of 1. you do it 4 times frequency of 4.. it has nothing to do with colour. (frequency is measured by how many waves pass through a certain point per second).

Also the smaller the wavelength the higher energy that wave possesses. eg gamma rays have incredably small wavelengths and high energy, where as ir has large wavelength and low energy.

heres a great picture explaining what i mean, short (high energy) wavelengths on left, long (low energy) wavelengths on the right.

The website has a typo as prototype said. That is a 405nm laser "violet" or "purple".

hope that helped -Adrian

Actually, frequency and wavelength are both equally related to color, because the speed of light is fixed/constant. You have it backwards, speed has nothing to do with wavelength in vacuum, speed is the same for all wavelengths in vacuum. Frequency changes with wavelength. Since the waves are always moving the same speed, the wavelength and frequency are inextricably linked, both indicate color.

Not exactly. A spectroscope is used to define light's wavelength. A spectroscope works by breaking light into the wavelengths (or spectra) that make it up. Some spectroscopes are made of diffraction grating- a material that has lots of little parallel lines that are approximately one wavelength apart. There may be 35,000 of these little lines in one inch of the material. When light hits the lines, it bends. Different wavelengths (colors) of light bend by different amounts, so it splits the light into its colors. Other spectroscopes are made of prisms- as light passes through the glass, the different wavelengths slow down by different amounts and are bent into their colors. Scientists can tell the elements present in a star by looking at its light through a spectroscope. Each element will have its own unique spectral lines of color, just as people each have a unique fingerprint..... meaning the only info you need to "find" the colour of light is the wavelength!

BTW source from wikipedia: Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths..... which is exactly what I said!

-Adrian

You have some things mixed up.

You said: "actually wavelength is an exact measure of the colour of light (as well as its energy, velocity and other non related units). frequency of the light has nothing to do with the colour." This is not correct. We use light in air, so we assume n=1 all the time. Therefore the speed of light never changes with wavelength. You said wavelength determines speed, and while that is true in mediums that have refractive indices that don't equal one, we're in air, where refractive index is essentially one. Since that's the regime we're in, where the speed of light is completely independent of wavelength, frequency of light is a perfect indicator of color, exactly as good an indicator as wavelength is.

Now if you go into a solid, like a prism, yes, then speed changes with wavelength, as indicated by the refractive index. This is, like you say, how a prism works: high refractive index, which means higher dispersion, which means increased change in refractive index with wavelength, which means higher differential refraction.

A diffraction grating works in a completely different way though, totally different from refraction.

But yeah, thanks for trying to explain the spectroscope. I know how this stuff works, but I certainly appreciate your effort anyway.

 

[bobhaha]

kk cool... BTW I meant you can use the wavelength to work out other things such as velocity, energy... ect. so ya

 

[Lasher]

Great info guys thank you very much!

Does anyone have a more detailed version of that Color by Wavelength chart that bobhaha posted?

I think one similar to that with all the most common laser colors and wavelengths seen here on the forums typed in would be a great help to new members and should maybe be put up and stickied so that when someone new reads a post about a laser for sale and it just says 405nm they will be able to look at that chart and know what color that laser is.

I'm sure for all the old timers here you know just by looking but to us noobs it still takes referring back to some kind of chart to know the color were dealing with. Just a thought

Thanks again for all the great info.

Lasher

 

[Greenmechanic]

Here is one I made up when I first started this hobby. I don't know how to sticky it.:undecided: If it seems like it will suit noobs needs(I know I've used the h#LL out of it), somebody feel free to use it.
Direct link http://i238.photobucket.com/albums/ff253/mechman_02/Lasercolorsbynm.jpg

[/IMG]

 

[Deleted member 8382]

frequency of the light has nothing to do with the colour.

where did you got that idea from? you can tell the color of the light by the wavelenght or the frequency!

 

[Lasher]

Greenmechanic,

Thanks that is a great chart. I hope it does end up in a FAQ section or something as I think it will be very helpful.

Lasher

 

[bobhaha]

heres another one... it shows the colour of the wavelength... and shows the type of laser needed to make that colour!

where did you got that idea from? you can tell the color of the light by the wavelenght or the frequency!

:wtf: How do you find the colour of light from the frequency??