A laser pulse with wavelength 540 nm contains 4.40 Mj of energy. How many photons are in the laser pulse?
To determine the number of photons in a laser pulse, we need to use the equation:
Energy of a photon (E) = Planck's constant (h) * Speed of light (c) / Wavelength of the laser pulse (λ)
First, we need to convert the energy of the laser pulse from Mega-joules (Mj) to joules (J). Since 1 Mega-joule is equal to 1,000,000 joules, we have:
Energy = 4.40 Mj * 1,000,000 J/Mj
Energy = 4,400,000,000 J
Now, we can use the equation to find the energy of a single photon:
E = h * c / λ
Where:
E = Energy of a photon (in joules),
h = Planck's constant (6.626 x 10^-34 J s),
c = Speed of light (3 x 10^8 m/s),
λ = Wavelength of the laser pulse (in meters).
Let's do the calculations:
E = (6.626 x 10^-34 J s) * (3 x 10^8 m/s) / (540 x 10^-9 m)
E = 3.66 x 10^-19 J
Now we know the energy of a single photon is 3.66 x 10^-19 J.
To find the number of photons in a laser pulse with a given energy, we can use the formula:
Number of photons = Energy of laser pulse / Energy of a single photon
Number of photons = 4,400,000,000 J / 3.66 x 10^-19 J
Number of photons ≈ 1.20 x 10^28 photons
Therefore, there are approximately 1.20 x 10^28 photons in the laser pulse.
E = hc/wavelength. Substitute and solve for E = energy of one photon. Then,
E of 1 photon x #photons = 4.40E6 J.
Solve for # photons.