electrical

# electrical - EE 4770 Lecture Notes Generated from file...

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

EE 4770 Lecture Notes Generated from file lsli08.dvi. This page was generated using an imperfect translator. Text may be poorly positioned and mathematics will be barely readable. Illustrations will not show at all. If possible, view the PostScript or PDF versions of these notes. 08-1 Light * * 08-1 Definition: wave or particle of electromagnetic energy. Consider photon character of electromagnetic energy. Photon energy, E = ch__, where c = 2:99792458 109 _m__s, h = 6:6260755 1034 J s, and is the particle wavelength. Effect of Photon Type of effect depends upon photon energy, : : : : : :which is proportional to its frequency. Amount of effect depends upon number of photons. Our Concerns Need to measure photon energy and "amount." Therefore, need to know effect of photons on materials. Useful Photons When a photon strikes an atom, : : : : : :it might cause an electron to change energy levels. Energy level changes to be considered: - Valence to conduction in a semiconductor.

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

View Full Document
- Bound-to-an-atom to free-of-the-atom. 08-1 EE 4770 Lecture Transparency. Formatted 8:22, 5 February 1999 from lsli08* *. 08-1 08-2 Optical Units * * 08-2 Two Types of Units - Radiometric units. Based on actual photon energies. - Photometric units. Based on human perception. Examples of When Used Radiometric units might be used : : : : : :find out how much an item would be warmed by light. Photometric units might be used : : : : : :for designing room lighting. 08-2 EE 4770 Lecture Transparency. Formatted 8:22, 5 February 1999 from lsli08* *. 08-2 08-3 Radiometric Units * * 08-3 Consider a light source. Radiant Energy, Q, total energy. Could be found by totaling energy of each photon over a specified period of time.
Popular units: erg, joule, kilowatt-hour. This unit is not usually used to measure light. dQ Radiant Flux, = _____, total power. dt Total amount of light being radiated from a source per unit time, t. Popular units: erg/second, watt (sometimes called light-watt). d Irradiance, E = _____, flux density. dA Amount of light per unit area, A. Popular unit: watt per square meter. d Radiant Intensity, I = _____. d! Amount of light per unit solid angle, !. Popular unit: watt per steradian. 08-3 EE 4770 Lecture Transparency. Formatted 8:22, 5 February 1999 from lsli08* *. 08-3 08-4 * * 08-4 Steradian Not-very-familiar-unit: steradian, a unit of solid angle. Abbreviation for this pseudo dimension: sr . Consider a sphere of radius 1. Paint a circle on the sphere of area 1. The circle would subtend one steradian of solid angle. The entire surface of a sphere (of any radius) is 4ss steradians.

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

View Full Document
Example A light source radiates uniformly in all directions. Its radiant flux is = 1 W. Find the radiant intensity and irradiance at a distance of 1 m and 3:048 m. At 1 m:
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 07/18/2011 for the course EE 4770 taught by Professor Staff during the Fall '99 term at LSU.

### Page1 / 19

electrical - EE 4770 Lecture Notes Generated from file...

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

View Full Document
Ask a homework question - tutors are online