# Chemical Forums

## Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: zerox0o on September 19, 2009, 03:43:47 PM

Title: Calculate the longest possible wavelength, in nanometer...
Post by: zerox0o on September 19, 2009, 03:43:47 PM
If it takes   3.92 × 10−19 J   of energy to eject an electron from the surface of a certain metal, calculate the longest possible wavelength, in nanometers, of light that can ionize the metal.

How do I do this? I am really clueless... ???

thank you!!!
Title: Re: Calculate the longest possible wavelength, in nanometer...
Post by: DrCMS on September 19, 2009, 03:53:38 PM
How do you calculate the energy of light of a particular wavelength?  Hint Planck's constant is needed.
Title: Re: Calculate the longest possible wavelength, in nanometer...
Post by: zerox0o on September 19, 2009, 04:00:46 PM
How do you calculate the energy of light of a particular wavelength?  Hint Planck's constant is needed.

(energy) = (Planck constant)(frequency) - (work function)

(speed of wave) = (frequency)(wavelength)

E = hc/λ - φ
λ = hc/(E + φ)

k i got it! thanks :D