An electron of a hydrogen atom falling from n=3 in the excited state to back to ground state gives off about 12eV. what form the "light" will it give off?

Answer 1

I would do this.
1/wavelength = R(1/1 - 1/9)
R you can find in tables in your book or on the web. Calculate wavelength and from the wavelength look in your book or on the web for the spectrum and see where that wavelength falls.