(a) Define ionization potential. (b)(i) State the three types of emission spectra. (ii) Name one source each which produces each of the spectra stated in (b)(i). (c) In an x-ray tube, electrons are accelerated the target by a potential difference of 80 A Calculate the: (i) speed of the electron; ii) threshold wavelength of the electron. [h=6.6 x 10\(^{-34}\) Js; e = 1.6 x 10\(^{-19}\) C; Me = 9.1 x 10\(^{-31}\) d) An x-ray photon of frequency 4.5 x 10\(^{-18}\) strikes an. electron, assumed to be at rest. If t electron absorbs all the photon energy, calculate the speed acquired by the electron. [ h = 6.6 x 10\(^{-34}\) Js; Me = 9.1 x 10\(^{-31}\) kg ]
Explanation
a) Ionization potential V is the potential energy required to remove an electron from an atom completely to infinity from ground state. (b)(i) The three types of emission are - band spectrum - continuous spectrum and - line spectrum. (ii) Sources of each emmision spectrum are: - Band spectrum - from molecules or carbon(IV) oxides in a discharge tube. - Continuous spectrum - from sun, solids and liquids. - Line spectrum - from atoms in gases such as hydrogen or neon in a discharge tube. (c)(i) eV =\(\frac{1}{2} mV^2\) v = \(\sqrt{\frac{2 \times 1.6 \times 10^{-19} \times 80 \times 10^3}{9.1 \times 10^{-31}}}\) = \(\sqrt{2.81 \times 10^{16}}\) = 1.68 x 10\(^8 ms^{-1}\) (ii) \(\pi = \frac{h}{mv} = \frac{6.6 \times 10^{-31}}{9.1 \times 10^{-31} \times 1.68 \times 10^8}\) = 4.32 x 10\(^{-12}\)m
