Planck's Constant: Chemistry

Question

Calculate the wavelength (in nm) of a photon of light with an energy of 3.56×10^-20 J.

Answer 1

E = hc/λ ⇒

 

λ = hc/E = (6.626 x 10^-34 Js)(3.00 x 10⁸ m/s) / (3.56 x 10^-20 J) ≅ 5.58 x 10^-6 m = 5580 nm 

Answer 2

E = hν

E = energy

h = Planck's constant = 6.626x10^-34 J-sec

ν = frequency = c/λ = speed of light/wavelength = 3x10⁸ msec^-1/λ

 

Substituting into E = hν

E = hc/λ

3.56x10^-20 J = (6.626x10^-34 Jsec)(3x10⁸ msec-1)/λ

λ = (6.626x10^-34 Jsec)(3x10⁸ msec^-1)/3.56x10^-20 J) = 5.58x10^-7 m = 558 nm