(a) The electron kinetic energy is

which can be converted into Joule by keeping in mind that

So that we find

The kinetic energy of the electron is related to its momentum p by:

where m is the electron mass. Re-arranging the equation, we find

And now we can use De Broglie's relationship to find its wavelength:

where h is the Planck constant.
(b) By using the same procedure of part (a), we can convert the photon energy into Joules:

The energy of a photon is related to its frequency f by:

where h is the Planck constant. Re-arranging the equation, we find

And now we can use the relationship between frequency f, speed of light c and wavelength

of a photon, to find its wavelength: