METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small...

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METR 415/715 Monday 2/4/2013

Transcript of METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small...

Page 1: METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small “packets” ot EM radiation that behave like particles.

METR 415/715

Monday 2/4/2013

Page 2: METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small “packets” ot EM radiation that behave like particles.

EM Radiation can be considered as particles as well as waves

• Small “packets” ot EM radiation that behave like particles

• Called “photons”

• E= Energy carried by photon• h= Planck’s constant = 6.626 X 10-34 J s• ν = Frequency

Page 3: METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small “packets” ot EM radiation that behave like particles.

Photon’s are “indivisible”

• As 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 windshield”

• If monochromatic radiation of wavelegth λ deposits F Watts per unit area on a surface, then this corresponds to F/hν photons per unit area per unit time

Page 4: METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small “packets” ot EM radiation that behave like particles.

Flux (F)

• Flux is the rate at which radiation is incident on, or passes through a flat surface

• Expressed in units of Wm-2 for “broadband” radiation (radiation of many wavelengths)

• The flat surface may be oriented in any direction

• Monochromatic flux (Fλ) has units of Wm-2 per unit wavelength, Wm-2μm-1

Page 5: METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small “packets” ot EM radiation that behave like particles.

Broadband Flux

• Encompasses a range of wavelengths. Defined as

Page 6: METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small “packets” ot EM radiation that behave like particles.

Intensity

• Tells you in detail both the strength and the direction of various sources contributing to the incident flux on a surface

• Spherical coordinates are useful in describing intensity

• Coordinates are Φ (azimuth) and θ (elevation)

Page 7: METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small “packets” ot EM radiation that behave like particles.

Solid angle

• Measured in steradians (sr)• Steradian – (ratio of area in a solid angle

compared to the area of a sphere of unit radius) 4π r2, where r=1

• In differential form, a steradian would be:

Page 8: METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small “packets” ot EM radiation that behave like particles.

Reflection refraction scattering

Page 9: METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small “packets” ot EM radiation that behave like particles.

Refraction of light in a raindrop

Page 10: METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small “packets” ot EM radiation that behave like particles.

Scattering

Page 11: METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small “packets” ot EM radiation that behave like particles.

Reflectivity of water

Page 12: METR 415/715 Monday 2/4/2013. EM Radiation can be considered as particles as well as waves Small “packets” ot EM radiation that behave like particles.

Absorption

• “Imaginary” part of the index of refraction• Gives you information on how much

absorption will take place