posted by mel .
calculate the max wavelength of light capable of removing an electron for a hydrogen atom from the energy state characterized by the following :
n=2 in nm
n=4 in nm
E = 2.180 x 10^-18 J/n2 where n is the principle quantum number of 2 or 4 for your two problems.
Then E = hc/lambda. h is Planck's constant, c is speed of light, lambda is wavelength IN METERS. Solve for lambda.