Question

On its highest power setting, a 770-watt microwave oven heats a bowl of spaghetti. (a) Find the average intensity of the microwaves, given they are absorbed over a circular area 23 cm in diameter. W/m2 (b) What is the peak electric field strength of the microwave? V/m (c) What is its peak magnetic field strength? T

Answer 1

a.)

Average intensity is given by,

I = P/A

here, P = Power = 770 W

A = area of circle = pi*d^2/4

d = diameter of circle = 23 cm = 0.23 m

then, I = 770/(pi*0.23^2/4)

I = 18532.98 W/m^2

I = 1.85*10^4 W/m^2

b.)

also, I = 0.5*c*e0*Emax^2

here, c = speed of light = 3*10^8 m/s

e0 = 8.85*10^-12

Emax = peak electric field = sqrt(2*I/(c*e0))

Emax = sqrt[(2*1.85*10^4)/((3*10^8)*(8.85*10^-12))] = 3733

Emax = 3.73*10^3 V/m

c.)

now, Bmax = Emax/c

Bmax = peak magnetic field strength = 3733/(3*10^8)

Bmax = 1.24*10^-5 T