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METR 415/715Monday 2/4/2013EM Radiation can be considered as particles as well as wavesSmall packets ot EM radiation that behave like particlesCalled photons

E= Energy carried by photonh= Plancks constant = 6.626 X 10-34 J s = Frequency

Photons are indivisibleAs text states on page 31 very low intensity light deposits discrete packets of energy on a surface in a manner analogous to the occasional random splashes of fat raindrops on your windshieldIf monochromatic radiation of wavelegth deposits F Watts per unit area on a surface, then this corresponds to F/h photons per unit area per unit time

Flux (F)

Flux is the rate at which radiation is incident on, or passes through a flat surfaceExpressed in units of Wm-2 for broadband radiation (radiation of many wavelengths)The flat surface may be oriented in any directionMonochromatic flux (F) has units of Wm-2 per unit wavelength, Wm-2m-1Broadband FluxEncompasses a range of wavelengths. Defined as

IntensityTells you in detail both the strength and the direction of various sources contributing to the incident flux on a surfaceSpherical coordinates are useful in describing intensityCoordinates are (azimuth) and (elevation)Solid angleMeasured in steradians (sr)Steradian (ratio of area in a solid angle compared to the area of a sphere of unit radius) 4 r2, where r=1In differential form, a steradian would be:

Reflection refraction scatteringRefraction of light in a raindrop

Scattering

Reflectivity of water

AbsorptionImaginary part of the index of refractionGives you information on how much absorption will take place