Predict the colours of the following materials, given their band-gap energies (in parentheses):
GaAs (1.43 eV), HgS (2.1 eV), and ZnS (3.6 eV). Show all your calculations.
Use: h = 6.626 x 10-34 J.s
1 eV = 1.6 x 10-19 J
Table 14.1 Colour,frequency,and energy oflight
Colour
1/nm
v/(1014Hz)
v/104cm-1
E/eV
E/kJmol-
Infrared Red Orange Yellow Green Blue Violet
>1000 700 620 580 530 470 420 300
<3.00 4.28 4.84 5.17 5.66 6.38 7.14 10.0
<1.00 1.43 1.61 1.72
<1.24 1.77 2.00 2.14 2.34
<120 171 193 206
1.89
226 254 285 400
2.13 2.38 3.33
2.64 2.95 4.15
Near ultraviolet
Far ultraviolet
<200
>15.0
>5.00
>6.20
598
Data:J.G.Calvert and J.N.Pitts,Photochemistry.Wiley,New York1966