The light produced by the electron in strontium has a wavelength of 608 nm. how much energy must be added to strontium to get it to produce this wavelength

According to Einstein the energy of photon is given by the equation,

E = hν = h . c/λ

where h is Planck's constant, c is the speed of light, ν is the frequency of light and λ is the wavelength of light.  

Given, wavelength = 608 nm = 608 x 10⁻⁹ m  

Conversion factor: 1 nm = 10⁻⁹ m  

c = 3 x 10⁸ m/s

h = 6.626× 10⁻³⁴ J.s

Substituting the data into the equation we get,  

E = h . c/λ

E = 6.626× 10⁻³⁴ J.s x (3 x 10⁸ m/s) / 608 x 10⁻⁹ m  

E =  3.27 x 10⁻¹⁹J

3.27 x 10⁻¹⁹J  energy must be added to strontium to get it to produce 608 nm wavelength.