(a) (i) Define atomic spectra. (ii) Differentiate between emission spectra and absorption spectra. (b)
The diagram above illustrates an electron transition from energy level n = 3 to n = 1. Calculate the: (i) energy of the photon (ii) frequency of the photon (ii) wavelength of the photon [h = 6.6 x 10\(^{-34}\)J s, c = 3.0 x 10\(^8\) ms\(^{-1}\); 1 ev = 1.6 x 10\(^{-19}\) J]
c)(i)Differentiate between soft x-rays and hard x-rays (ii) Draw the circuit symbol for a p-n junction diode. (iiii) Give the reason for doping a semiconductor material
Explanation
(a) The emission of light from a substance when its excited electrons move to a lower energy level. OR Distinct/separate bright lines of light of definite frequency/wavelength (emitted from vapourised atoms) (ii) Emission spectra is the pattern of light displayed when electrons jump from a higher energy level to a lower energy level, while absorption spectra is the displayed pattern of wavelengths absorbed by the gas.
(b) \(\Delta\)E = E\(_i\) - E\(_f\) = -1.51 + 13.6 = 12.09 eV = 12.09 x 1.6 x 10\(^{-19}\) J = 1.934 x 10\(^{-18}\) J (ii) \(\Delta\)E- hf f = \(\frac{\Delta E}{h}\) = \(\frac{1.934 \times 10^{-18}}{6.6 \times 10^{-34}}\) f = 2.93 x 10\(^{15}\)Hz
(ii) c = f\(\lambda\) \(\lambda\) = \(\frac{3 \times 10^8}{2.93 x 10^{13}}\) = 1.023 x 10\(^{-7}\)m
(c) (I) Soft x-rays are those with longer wavelengths/lowNer penetrating/less energy while hard x-rays are those with shorter wavelengths/higher penetrating power more energy.
(iii) To increase the electrical conductivity/reduce electrical resistivity of the semiconductor.
