mse21 - Chapter 21: Optical Properties ISSUES TO ADDRESS....

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Chapter 21 - 1 ISSUES TO ADDRESS. .. • What happens when light shines on a material? • Why do materials have characteristic colors? • Optical applications: -- luminescence -- photoconductivity -- solar cell -- optical communications fibers • Why are some materials transparent and others not? Chapter 21: Optical Properties Chapter 21 - 2 Optical Properties Light has both particulate and wavelike properties – Photons - with mass λ = ν = Δ hc h E m/s) 10 x (3.00 light of speed c ) s J 10 62 . 6 ( constant s Planck' frequency wavelength energy 8 34 = = = ν = λ = Δ x h E
Background image of page 1

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

View Full DocumentRight Arrow Icon
2 Chapter 21 - 3 Refractive Index, n Note: n = f ( λ ) Typical glasses ca. 1.5 -1.7 Plastics 1.3 -1.6 PbO (Litharge) 2.67 Diamond 2.41 medium) in light of (velocity vacuum) in light of (velocity v c • Transmitted light distorts electron clouds. • Light is slower in a material vs vacuum. n = refractive index + no transmitted light transmitted light + electron cloud distorts Selected values from Table 21.1, Callister 7e . --Adding large, heavy ions (e.g., lead can decrease the speed of light. --Light can be "bent" Chapter 21 - 4 Total Internal Reflectance φ φ′ = sin sin n n n ’(low) n (high) n > n 1 φ c φ ' 1 φ angle critical angle refracted angle incident = φ = φ′ = φ c i i reflected internally is light for 90 when occurs c i i c φ > φ ° = φ′ φ
Background image of page 2
3 Chapter 21 - 5 Example: Diamond in air • Fiber optic cables are clad in low n material for this reason. o o 5 . 24 41 . 2 1 sin sin 1 sin 90 sin 1 41 . 2 sin sin = φ = φ φ = φ = φ φ′ = c c c c n n Chapter 21 - 6 • Incident light is either reflected, absorbed, or transmitted: S R A T o I I I I I + + + = Light Interaction with Solids • Optical classification of materials: Adapted from Fig. 21.10, Callister 6e . (Fig. 21.10 is by J. Telford, with specimen preparation by P.A. Lessing.) single crystal polycrystalline dense polycrystalline porous Transparent Translucent Opaque Incident: I 0 Absorbed: I A Transmitted: I T Scattered: I S Reflected: I R
Background image of page 3

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

View Full DocumentRight Arrow Icon
4 Chapter 21 - 7 Absorption of photons by electron transition: • Metals have a fine succession of energy states. • Near-surface electrons absorb visible light. Adapted from Fig. 21.4(a), Callister 7e . Optical Properties of Metals: Absorption Energy of electron I n c i d e t p h o Planck’s constant (6.63 x 10 -34 J/s) freq.
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/18/2010 for the course ME 2580 taught by Professor Vandenbrink during the Spring '08 term at Western Michigan.

Page1 / 15

mse21 - Chapter 21: Optical Properties ISSUES TO ADDRESS....

This preview shows document pages 1 - 5. Sign up to view the full document.

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