Answer:
In 3.5 x 10^(15) J of energy there are 9*10^(33) photons.
Step-by-step explanation:
To solve this problem, we need two equations.
The equation of light velocity, wich is a relation between wavelenght and frecuency.
c=λν (1)
where:
- c: speed of light = 3 × 10^8 [m/s]
- ν: frecuency [1/s]
- λ: wavelenght of wave [m]
The Photoelectric Effect equation, that refers to the energy absorbed or emanate by ONE photon.
E = hν (2)
where:
- h : Planck´s constant = 6,626*10^{-34} [J.s]
- ν: frecuency of radiation [s]
- Ef: energy of one photon [J]
The first we do is to calculate the frecuency of the flash using equation (1). The wavelenght of the flash is 510 nm = 510 * 10^(-9) m
c=λν........................ ν= c/λ = 3 × 10^8 [m/s]/ 510 * 10^(-9) m = 5,88 * 10^(14) 1/s
Note: small wavelenghts always have big frequencies
Now, we use the photoelectric effect equation to calculate the amount of energy that ONE photon can abosrb.
E = hν ..................... E = 6,626*10^{-34} [J.s] * 5,88 * 10^(14) 1/s =3,9 * 10^(-19) J
To know the number of photons, we just have to divide the TOTAL amount of energy between the energy of ONE photon. So:
# photons = 3.5 x 10^(15) J / 3,9 * 10^(-19) J = 9*10^(33) photons.