# Calculating Laser Beam Power and Wave Crests per Second at 632.8nm Wavelength

• stunner5000pt
In summary, to find the number of wave crests per second passing through any point in the laser beam, you need to use the formula f=c/λ, where c is the speed of light and λ is the wavelength. By plugging in the given values, we can calculate the frequency, which is the number of wave crests per second. However, there seems to be some confusion about the terms used in the conversation, such as "energy per photon" and "energy per second". Clarification may be needed in order to fully understand the problem and its solution.
stunner5000pt
A laser emits light at a wavelength of 632.8nm. The laser beams power is 1.0mW. Find the number of wave crests per second passing through nay point in the beam.

so f = $$\frac{c}{\lambda} = 2.1 * 10^ -15$$

(while you're at it tell me what's wrong with my code too, please)

f = c /lambda = 2.1x 10^-15 Hz

so then i know the frequency and the inverse of this is the period. The number of crests per second is the period (?) so the frequency gives the number of crests per second??

Last edited:
Hi stunner,

You know the power, which is the energy per second passing by.
You know the energy of a single photon (??wave crests??) from $E=h\nu$.
Hope this is the info you need and may use.

Galileo said:
Hi stunner,

You know the power, which is the energy per second passing by.
You know the energy of a single photon (??wave crests??) from $E=h\nu$.
Hope this is the info you need and may use.

SO since P = E / t which is PER second and hf would give the energy per second.

So HF is the number of photons (crests) passing throiugh the beam at one second?

Am i right here? Or have i misinterpreted something

P (power) is energy per second (given).
hf is the energy per photon (given).
So the number of photons passing by per second is...

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