A parallel-plate air capacitor is made from two plates 0.200{\rm m} square, spaced 0.800 {\rm cm} apart. It is connected to a 120 {\rm V} battery. If the plates are pulled apart to aseparation of 1.60 {\rm cm}, suppose the battery remains connected while theplates are pulled apart. What is the capacitance?

C =2.21×10−11{\rm F}

Part B

What is the charge on each plate?

Enter your answer as two numbers, separated with a comma.

Part C

What is the electric field between theplates?

E =7500 {\rm V/m}

Part D

What is the energy stored in thecapacitor?

U =1.59×10−7{\rm J}

A)  C = 4.425 10⁻¹³ F,  B) Q = 6.31 10⁻¹¹ C,  C)  E = 8.9 10⁴ N / C,  

D)  u_{E} = 3.19 10⁻⁹ J

Explanation:

Part A. Capacitance is

           C = ε₀ A / d

in this case distance is d = 0.800 cm = 0.800 10⁻² m and the area of the plates is x = 0.200 cm= 0.2 10⁻² m, all the quantities must be in the SI system for the result to be in Farads

           A = x²

           A = (0.2 10⁻²)²

           A = 4 10⁻⁶ m

let's calculate

          C = 8.85 10⁻¹² 4 10⁻⁶ / 0.8 10⁻²

          C = 44.25 10⁻¹⁴ F

          C = 4.425 10⁻¹³ F

Part B. The charge on each plate is

          Q = C ΔV

           Q = 4.425 10⁻¹³ 120

           Q = 6.31 10⁻¹¹ C

Part C. the electric field of a plate is

           E = σ / 2ε₀

where the charge density is

            σ = Q / A

we substitute

             E =

let's calculate

             E =

             E = 8.9 10⁴ N / C

Part D. stored energy

              = ½ C V²

               u_{E} = ½ 4.425 10⁻¹³ 120²

               u_{E} = 3.19 10⁻⁹ J

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.