Question

Week 7 The optical properties of nonmetallic materials depend strongly on their bandgap. Planck's constant (เ) İSha4.135 x 10asevs and the speed oflight(c) is c 3x10"m/s. The wavelengths of light in the visible spectrum are: Violet light, A-04-0425pm Blue light, λ-0424-0.49μm Green light, λ-049-0.55μm Yellow light, λ :0.55-0.56μm Orange light, 2-0.56-0.65um Red light, 2 -0.65-0.7ym Question S a) What is the maximum bandgap that a material can have and remain fully opaque? What is the minimum bandgap a material can have and be fully transparent (not coloured)? b) a What colours of vistble light if anvy) are absorbed in a non-metalic material with a bandgap of 2.1 ev? a) What colours of visible light id any) are transmitted in a non metalic material with a bandgap of 2.8 ev? Question 6: The metal Copper, and the semiconductor Cadmium Sulfide (Cds, Bandgap-2.4ev) are both yellow in colour, but in each case, the physical origin of the colour is different a) Which colours in the visible spectrum are absorbed by the CdS? b) Which colours pass through the Cds? c) Which colours in the visible spectrum are absorbed by surface of the metallic Cu? d] Which colours pass through the metallic Cu? e) Why is Cu not silvery in colour?

Answer 1

ven (Uv) yeuloul Orange u E-hc_ - 14089 ev #Hou band gap, thanuu will be watLual Camscanner

oS . faa silico nhon the band ? n u 2.lev enc vi.ible Lo. Haue yeuau oud be 1.tu Sra 0 aun oudau b) F raw mittion 2.4 ev and above Hentu abi oho uld se 2.tav andl lou Scanned with CamScanner c). A, Cu bund CS

banet e) 4: most metal aprenu rīlveťn colou ·い!vu mulaa Csucha alum Scanned with CS CamScanner
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