ENGRI111_hw3_SOLN - ENGRI 111 Homework 3 Solutions Material...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
ENGRI 111 Homework 3 Solutions Material E g /eV Color C (diamond) 5.4 Clear ZnS 3.6 Clear ZnO 3.2 Clear CdS 2.4 Orange-yellow HgS 2.1 Red-orange GaAs 1.4 Black 1. The above-listed materials are all insulators (diamond) or semiconductors (everything after), and the mechanism responsible for observed colors is the transmission of light through the material. Since the first three materials (diamond through ZnO) have bandgaps greater than all visible photon energies (1.7-3.1eV), they do not absorb any visible light and allow all wavelengths to pass through. This is responsible for the clear (or white) appearance of these materials. CdS absorbs all wavelengths above its bandgap and only allows photons of energies less than 2.4eV to pass. The mix of these transmitted photons create an orange-yellow color. HgS absorbs light with energies greater than 2.1 eV and allows photons with energies less than 2.1eV to pass producing a red-orange color. GaAs absorbs all visible wavelengths and appears black. There was a lot of confusion on the mechanisms responsible for the color of metals, semiconductors, and insulators. For that reason, if your answers differ from the ones
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This homework help was uploaded on 02/03/2008 for the course ENGRI 1110 taught by Professor Giannelis during the Fall '07 term at Cornell University (Engineering School).

Page1 / 3

ENGRI111_hw3_SOLN - ENGRI 111 Homework 3 Solutions Material...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online