Laser produces a light of wavelength 575 nm How many photons of light would have to strike a material for the material to absorb 55.1 kJ?

E = h * f

E = energy

h = Planck's Constant

f = frequency

c = f * w

c = speed of light

f = frequency

w = wavelength

c = f * w

f = c / w

E = h * f

E = h * c / w

That's the energy of a single photon of a particular wavelength

E * n = T

n = number of photons

T = total energy

T = 55.1 kJ = 5.51 * 10 * 10^3 Joules = 5.51 * 10^4 Joules

w = 575 nm = 575 * 10^(-9) m = 5.75 * 10^(-7) m

c = 3 * 10^(8) m/s

h = 6.626 * 10^(-34) m^2 * kg / s

T = n * E

T = n * h * c / w

5.51 * 10^4 Joules = n * 6.626 * 10^(-34) * 3 * 10^(8) / (5.75 * 10^(-7)) [m^2 * kg * m / (s * s * m)]

5.51 * 10^4 = n * (6.626 * 3 / 5.75) * 10^(-34 + 8 + 7)

5.51 * 10^4 = n * (19.878 / 5.75) * 10^(-19)

(5.51 * 5.75 / 19.878) * 10^(4 + 19) = n

1.59384746956 * 10^(23)

1.59 * 10^(23) photons

E = Nhf = Nhc/λ

N = Eλ/(hc) ≈ 1.59x10^23