A question about lasers

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Stofsk
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#1 A question about lasers

Post by Stofsk »

Let's say we've got your typical sci-fi laser gun. I have two questions:

1. Does the laser beam make a sound, or is it soundless? If it makes a sound, what kind would it make? A gun-like 'crack!', or a 'pew-pew!' or what? If it doesn't make a sound, why not?

2. Is the beam visible or invisible? Obviously if it is a vacuum, the answer would be a quick no. But I'm talking about using a laser gun in an atmosphere. Would the beam be visible or not? If not, why not? Can it be made visible? If it is visible, can it be made invisible? If it can be visible, what kind of colour would the beam be?
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#2

Post by Ra »

I do believe that a high-intensity normal (that is, IR-wavelength) laser likely would produce a visible red beam in the atmosphere; however UV and X-ray lasers would produce invisible beams.

I don't know about sound, though; the laser might make a sound as the beam hits the target, or it might from heating the air around it. It would also depend on whether the laser was a beam or pulse type, I guess.
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#3 Re: A question about lasers

Post by Robert Walper »

Stofsk wrote:Let's say we've got your typical sci-fi laser gun. I have two questions:

1. Does the laser beam make a sound, or is it soundless?
A laser, despite their seeming complexity and technical nature, is just highly amplified light. You can expect the laser beam itself to make no sound. The only sounds you'll hear is the device creating the beam itself, and the interaction of the beam with whatever it hits.
If it makes a sound, what kind would it make? A gun-like 'crack!', or a 'pew-pew!' or what? If it doesn't make a sound, why not?
Addressed above.
2. Is the beam visible or invisible? Obviously if it is a vacuum, the answer would be a quick no. But I'm talking about using a laser gun in an atmosphere. Would the beam be visible or not? If not, why not? Can it be made visible? If it is visible, can it be made invisible? If it can be visible, what kind of colour would the beam be?
Lasers are focused and directed light, meaning the only way you'll see the laser beam is if particles within the beam reflect some of the light outwards, or you're having the beam pointed directly at you (not recommended).
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#4

Post by Comrade Tortoise »

Damn you walper you beat me to it
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#5

Post by Robert Walper »

Comrade Tortoise wrote:Damn you walper you beat me to it
:smile: Sorry, I couldn't resist the urge to look semi intelligent and informed about a nifty piece of technology.
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#6

Post by Destructionator XV »

While the laser itself won't be seen or make a sound, it effects will.

As it travels though the air, much of the energy will be absorbed by the air, and more so by the water vapour. As the water superheats, it can spread the light, making the trail visible (or leave a stream of steam) and will release sound as chemical reactions occur due to the heat.

The sound will be a crack sound.
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#7

Post by Josh »

Destructionator XV wrote:The sound will be a crack sound.
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#8

Post by Knife »

I would imagine if you were close to the emitter, you'd hear a buzzing sound of the power system much like a transformer station.
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