# How many photons per second does the laser emit?

## How many photons per second does the laser emit?

The power of a red laser (lambda=630 nm) is 3.5 watts (abbreviated W, where 1 W= 1 J/s)=

**pplantblues**- Posts : 109

Join date : 2008-11-14

## Re: How many photons per second does the laser emit?

I'm, not 100% sure this is right, but this is how I would solve it.

First, figure out the energy that one photon of red (630 nm) light has using Planck's equation.

E= hν

Energy (in joules)= Planck's constant (6.63 x 10

E= 6.63 x 10

E= 4.18 x 10

This is the energy in 1 photon of 630 nm light.

Since the problem gives us that the energy is 3.5 W or 3.5 J/s, we need to find out how many photons with the energy above we would need to produce 3.5 J. SO we divide:

3.5/(4.18 x 10-40) = 8.37 x 10

First, figure out the energy that one photon of red (630 nm) light has using Planck's equation.

E= hν

Energy (in joules)= Planck's constant (6.63 x 10

^{-34}) x frequency (in meters)E= 6.63 x 10

^{-34}(630 x 10^{-9}m)E= 4.18 x 10

^{-40}JThis is the energy in 1 photon of 630 nm light.

Since the problem gives us that the energy is 3.5 W or 3.5 J/s, we need to find out how many photons with the energy above we would need to produce 3.5 J. SO we divide:

3.5/(4.18 x 10-40) = 8.37 x 10

^{39}photons**funion987**- Administrator
- Posts : 146

Join date : 2008-11-09

## Re: How many photons per second does the laser emit?

This is what I got for an answer:

E=hc/landa=(6.626x10^-34 J/s)(3.00x10^8 m/s)/6.3x10^-7 m= 3.15x10^-19J

630nm x (10^-9/1 nm)=6.3 x 10^7 m

Since 1 W= 1 J/s

3.50 watts= 3.5 J/s

So 3.5 J/s / 3.15 x 10^-19= 1.11 x 10^-19 photons/s

Thanks for trying.

E=hc/landa=(6.626x10^-34 J/s)(3.00x10^8 m/s)/6.3x10^-7 m= 3.15x10^-19J

630nm x (10^-9/1 nm)=6.3 x 10^7 m

Since 1 W= 1 J/s

3.50 watts= 3.5 J/s

So 3.5 J/s / 3.15 x 10^-19= 1.11 x 10^-19 photons/s

Thanks for trying.

**pplantblues**- Posts : 109

Join date : 2008-11-14

## Re: How many photons per second does the laser emit?

You know what, I totally screwed that one up. Maybe it's best if I don't answer if I don'y know. Sorry.

**funion987**- Administrator
- Posts : 146

Join date : 2008-11-09

## Re: How many photons per second does the laser emit?

Don't worry about it ! You still rock

**pplantblues**- Posts : 109

Join date : 2008-11-14

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