(a) (i) Define atomic spectra. (ii) Differentiate between emission spectra and absorption spectra. (b) The...
(a) (i) Define atomic spectra.
(ii) Differentiate between emission spectra and absorption spectra.
(b)
The diagram below 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.