Question

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Problem 7 Two microwave frequencies are authorized for use in microwave ovens: 900 MHz and 2,560 MHz. a) On its highest power setting, a microwave oven can produce 1.00 kW of power onto a 30.0 by 40.0 cm area. What is the intensity in W/m2? b) Calculate the peak electric and magnetic field strength in these waves. c) The maximum safe intensity of microwaves for human exposure is 1.00 W/m. If a radar unit leaks 10.0 W of microwave radiation uniformly in all directions, how far away must you be in order to avoid unsafe levels of radiation? Assume that the power spreads uniformly over the arca of a sphere. Problem8 If you wish to detect details the size of atoms with EM radiation, it must have a wavelength ofabout this size. a) What is its frequency? b) What type of EM radiation is this? c) What is the smallest observable detail you can observe with a microscope that uses UV light of frequency 1.20x 10'5 Hz?

Answer 1

Question no 7 )

a )

given

P = 1 k W

= 1000 W

A = 30 x 40

= 1200 cm²

= 0.12 m²

here intensity I = P/A

= 1000 / 0.12

I = 8333.333 W/m²

and I_o = 2 x 8333.333

= 16.66 x 10³ W/m²   

b )

using I_o = e_oCE_o²

E_o= ( I_o/e_oC )^1/2

= ( 16.66 x 10³ / 8.85 x 10^-12 x 3 x 10⁸ )^1/2

E_o= 2504.985 V/m

c )

the distance d = ( P / 4 x 3.14 x I )^1/2

= ( 1000 / 4 x 3.14 x 8333.333 )^1/2

d = 0.09774 m

or

d = 9.774 cm