Number of photons emitted from a laser

In summary, a 35mW laser with a wavelength of 526nm emits approximately 1.9x10^17 photons per second. The energy of one photon can be calculated by using the frequency obtained from the wavelength.
  • #1
pat666
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Homework Statement


A 35mW laser produces 526nm green light.
What is the number of photons it emits each second?
1.9×1017
1.9×1018
1.0×1017
9.3×1016


Homework Equations





The Attempt at a Solution


I've been playing with E=hf and lambda = h/p ----- no success!
The textbook I am using doesn't have much on photons/photoelectric effect - nothing that helps me with this question at least. the "photon wavelength-momentum relation" is I think the most relevant to this question?? The textbook doesn't actually say what p is so I assumed number of photons but that's wrong since it doesn't work.

anyway need some help please.
 
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  • #2
Calculate the energy of one photon. You need to get the frequency from the wavelength.

ehild
 
  • #3
thanks ehild - solved the problem
 

1. How is the number of photons emitted from a laser calculated?

The number of photons emitted from a laser is calculated by multiplying the energy of each photon by the total energy output of the laser and dividing by the energy of a single photon. This calculation is known as the photon flux.

2. Does the number of photons emitted from a laser vary?

Yes, the number of photons emitted from a laser can vary depending on the energy input, the type of laser, and the efficiency of the laser. Additionally, external factors such as temperature and environmental conditions can also affect the number of photons emitted.

3. Can the number of photons emitted from a laser be controlled?

Yes, the number of photons emitted from a laser can be controlled by adjusting the energy input or using techniques such as Q-switching or mode-locking. These methods allow for precise control over the number of photons emitted and the duration of the laser pulse.

4. How does the wavelength of a laser affect the number of photons emitted?

The wavelength of a laser does not directly affect the number of photons emitted. However, the energy of each photon is inversely proportional to the wavelength, so a shorter wavelength laser will emit more energetic photons and thus, fewer photons will be needed to achieve the desired energy output.

5. Is the number of photons emitted from a laser constant over time?

No, the number of photons emitted from a laser can decrease over time due to factors such as degradation of the laser components or changes in the environment. Regular maintenance and proper use can help maintain a consistent number of photons emitted from a laser.

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