4.1 Rayleigh Scattering Flashcards
What is Rayleigh scattering?
The elastic interaction of radiation with a polarisable particle of size d
d «_space;wavelength
What is the equation between the power of the scattered light and the poynting vector?
P_scattered is prop. to w^4 N_Poyn
- Strong scattering for high frequency light
Why is the sky blue?
Blue light scatters the best from the sun in all directions
Why is the sky red in the evenings?
The light has travelled through a large proportion of the atomosphere (tangent to the earth) and the blue light has been scattered out
If the sun shines from the south, which direction is it polarised?
In the East-West direction (Ey component)
What type of scattering is observed when d approx. = wavelength?
Mie
What is Thomson scattering?
Free charge elastic scattering
Are Rayleigh and Thomson scattering dependent on frequency?
Rayleigh is prop. w^4
Thomson isn’t (it is a function of E)
What is Compton scattering?
Inelastic radiation scattering for very high velocity (v near c) particles
Why is the classical radius for an electron not a good estimate?
Because you need to consider QM and its wave behaviour
What is the equation for Compton scattering?
λ - λ’ = h/mc (1-cos(theta))
- Theta is the scattering angle of the radiation, not the particle
