Properties of light – A tool in Energy and Environmental

Physics

F. Sigernes

A trial lecture @ NTNU

A-M Ampère 1775-1836

C. F. Gauss 1777-1855

M. Faraday 1791-1867

J. C. Maxwell 1831-1879

OERSTED, H. C. 1777-1851

H. R. Hertz 1857 - 1894

M. Planck 1858 - 1947

A. Einstein 1879 - 1955

N. Bohr,1885-1962

Images are taken from search engine Google Images

A plane polarized sinusoidal wave!

color (Å) f (*1014 Hz) Energy (*10-19 J)

violet 4000 -    4600 7.5 - 6.5 5.0 - 4.3

indigo 4600 -   4750 6.5 - 6.3 4.3 - 4.2

blue 4750 -   4900 6.3 -   6.1 4.2 - 4.1

green 4900 -   5650 6.1 -   5.3 4.1 - 3.5

yellow 5650 -    5750 5.3 - 5.2 3.5 - 3.4

orange 5750 -    6000 5.2 - 5.0 3.4 - 3.3

red 6000 -    8000 5.0 - 3.7 3.3 - 2.5

VISIBLE LIGHT

DISRETE SPECTRA – ABSORPTION AND EMISSION

Intensity = Lifetime x # atoms energized

Nordkvist (2006)

CONTINOUS SPECTRA

BASIC PROPERTIES OF LIGHT

1) Light is electromagnetic waves – radiation2) It travels through empty space3) The speed is constant as a function of wavelength4) It is polarized depending on direction or rotation of E5) Light are emitted or absorbed in discrete chunks of energy 6) These packets of energy – photons - have energy E=hv7) Photons are released as a response to jumps in atomic / molecular energy levels (from Bohr’s model of the atom)8) Light is both a particle (photon) and a wave – depends how we observe it.9) Intensity is directly related to number of photons emitted from an object.10) Objects emits light in form of continuous or discrete spectra – depending mainly on density and temperature.

11) Light has wavelike behavior: it reflects, refracts, diffracts and interfere...

“Spectroscopy – is the tool to study the properties of objects.”

Basics of a hyperspectral imager – a camera that that images as a function of wavelength!

Basics of an airborne hyperspectral imager- bush broom (Zsolt, 2006)

VEGETATION – ROCKS - SEA & FRESH WATER

VEGETATION UNDER WATER

SCRIMPS: SKALL, SKALL IKKE!

REFERENCES

Douglas C. Giancoli, Physics for Scientists and Engineers, 2. ed. , Prentice Hall, Englewood Cliffs, New Jersey 07632, US, ISBN 0-13-669201-X, US, 1988.

Astronomy Notes (2004 Edition) by Nick Strobel, ISBN 0073122491, http://www.astronomynotes.com/

*Sample data are from experiments at Fiskeriforskning in Tromsø and from airborne campaigns at UNIS.