Arectangular slab with uniform volume charge density rho has thick- ness 2l in the x direction and infinite extent in the y and z direc- tions. let the x coordinate be measured relative to the center plane of the slab. for values of x both inside and outside the slab: (a) find the electric field e(x) (you can do this by considering the amount of charge on either side of x, or by using gauss’s law); (b) find the potential φ(x), with φ taken to be zero at x = 0; (c) verify that rho(x) = ε0∇ · e(x) and rho(x) = −ε0∇2φ(x).

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.

it was given as a lesson and guide for prayer.