Consider the light from a green laser pointer (wavelength = 532 nm).
What is the energy of 1 photon form this laser?
If the laser emits 1.30×10^-2 J during a pulse, how many moles
of photons are emitted during the pulse?
#1. E = hf = 6.62607015*10^-34 * 3.0*10^8/532*10^-9 = 3.7365*10^-19 J/photon
#2. 1.30*10^-2 J * 1photon/3.7365*10^-19 J/photon * 1mole/6.023*10^23photons = 5.776 *10^-8 moles
To find the energy of one photon from a laser, we can use the formula:
E = hc/λ
Where:
E is the energy of a photon,
h is Planck's constant (h ≈ 6.626 × 10^-34 J.s),
c is the speed of light (c ≈ 3.00 × 10^8 m/s),
and λ is the wavelength of the light.
For the given green laser pointer with a wavelength of 532 nm (or 532 × 10^-9 m), we can substitute these values into the formula to find the energy of one photon:
E = (6.626 × 10^-34 J.s × 3.00 × 10^8 m/s) / (532 × 10^-9 m)
Simplifying the expression:
E ≈ 3.739 × 10^-19 J
Therefore, the energy of one photon from the green laser pointer is approximately 3.739 × 10^-19 joules.
Moving on to the second part of the question, to determine the number of moles of photons emitted during a pulse, we can use Avogadro's constant (NA ≈ 6.022 × 10^23 mol^-1).
Given that the laser emits 1.30 × 10^-2 J (joules) during a pulse, we can calculate the number of photons by dividing the total energy emitted by the energy of one photon:
Number of photons = (1.30 × 10^-2 J) / (3.739 × 10^-19 J)
Simplifying the expression:
Number of photons ≈ 3.476 × 10^16 photons
To convert this to moles of photons, we divide the number of photons by Avogadro's constant:
Number of moles of photons = (3.476 × 10^16 photons) / (6.022 × 10^23 mol^-1)
Simplifying the expression:
Number of moles of photons ≈ 5.780 × 10^-8 mol
Therefore, during the pulse, approximately 5.780 × 10^-8 moles of photons are emitted from the laser.