Question

Suppose your center produced a solar cell with the first surface being a glass of index n = 1.5 which curiously has that value over the entire solar spectrum.

a) if unpolarized light falls on the glass surface at the Brewster angle, what fraction of the energy in the incident light is reflected from the glass?

b) suppose that the sunlight delivers irradiance (time-averaged Poynting vector) of 1 kW/m2 . Calculate the amplitude of the electric field in this sunlight.

c). Suppose 10% of the solar cell’s surface is covered with aluminum traces that reflect 100% of the sunlight, and the remainder of the active array area has reflectance of 20%. What is the pressure exerted by the 1 kW/m2 solar irradiance on this array at normal incidence?

kB = 1.38 x 10-23 J/o K

µ0 = 4π x 10-7 T m/A

h = 6.63 x 10-34 Js

Answer 1

a] At Brewster's angle, all the reflected light is perpendicularly polarized (s-polarized). Since the incident light is unpolarized and can be assumed to have equal perpendicular and parallel polarization light, only half of the energy of the incident light is reflected at Brewster's angle.

b] Time-averaged value of Poynting flux magnitude is related to Electric field amplitude by:

=> E_o = 868.32 V/m

this is the amplitude of electric field in the radiation.

c] Radiation pressure for a perfectly reflecting body is given by: P = 2I/c

for a reflecting body with reflectance 0.2, this is:

so, the pressure exerted by the radiation in this case will be:

.