The intensity of the sunlight that reaches Earth’s upper atmosphere is approximately 1400 W/m2. (a) What is the average energy density? (b) Find the rms values of the electric and magnetic fields. Some useful formulas: I = <> c, <>= 0 Erms2 = Brms2 /0, 0=8.854 x 10-12 C2/(N. m2) , 0= 4  x 10-7 T. m/A, c= 3 x 108 m/s.

(a) Average energy density is 4.67 × 10⁻⁶  J/m³

(b) The rms value of the electric field is 726.26 V/m

and the rms value of the magnetic field 2.42 × 10⁻⁶ T

Explanation:

The average energy density < u > is given by

< u > = I / c

Where I is the intensity and

c is the speed of light

From the question

I = 1400 W/m²

c = 3 × 10⁸ m/s

∴ < u > = 1400 W/m² /  3 × 10⁸ m/s

< u > = 4.67 × 10⁻⁶  Ws/m³ (NOTE: Ws = J)

< u > = 4.67 × 10⁻⁶  J/m³

This is the average energy density

(b) From the formula

From the question, = 8.854 × 10⁻¹² C²/N.m²

∴

This is the rms value of the electric field

For the rms value of the magnetic field

From

Then,

From the question, = 4π × 10⁻⁷ T.m/A

This is the rms value of the magnetic field

28. evolution

29. environment, survive, offspring  

explanation:

c)as speed changes, wavelength and frequency change.

everything changes!