Physics problem - pleaseeeee need help!

Question

I'm editing this problem because I was able to get a couple of the answers, but I still need help on the rest. An electromagnatic wave is traveling in vacuum with frequency 7 x 1014 Hz. The wave has average total energy density of 5.6 x 10-6 J/m3. (a) What is the speed of this wave? v = m/s * 300000000 OK (b) What is the wavelength of this wave? l = m * .0000004286286 OK (c) What is the maximum electric field of this wave? Emax = V/m HELP: Look for any equation that involves electric field amplitude and average energy density. Be careful - does this equation give you the maximum or rms value of the electric field? (d) What is the rms magnetic field of this wave? Brms = T (e) How much energy does a 1.8 m2 flat surface (perpendicular to the wave propagation direction) receive in 9 s? E = J * 27216 OK (f) How long does it take for this wave to travel from the sun to the earth? t = min (g) How many wavelengths of the wave fit in this distance? N = wavelengths

Answer 1

The formulas that you want for parts c) and d)  are

   u = (1/2) ε₀ E_{max²   and}

   u = (1/2) (1/μ₀ B_max²  

where ε₀ = 8.854 E-12   and μ₀ =  12.578 E-7

  Using u = 5.6E-6

  E_{max = 1124.7 V/m   and}

  B_max =  3.753 E-6 T  

   notice that B_max =  E_max/c  

  B_rms =   0.707 B_max =   2.651 E-6 T

 

The parts about time from sun to earth and the distance from sun to earth (measured in wave lengths) are easy to

work out.  The time works out be about 8 min and 20 s.