In: Physics
1 a) What is the approximate electric field strength and magnetic field strength of the electromagnetic waves radiated by a 60-W lightbulb, as measured 5.5 m from the bulb? You can assume that the bulb is 100% efficient in converting electrical energy to light energy.
b.) Incandescent light bulbs are very inefficient. Find the electric field strength and magnetic field strength assuming 5% efficiency.
Please show all work, thank you!
The intensity of the bulb at 5.5 m away is
The average intensity in terms of electric field is
where c is the speed of light and mu is the vacuum permeability
Therefore the electric field strength is
The magnetic field strength is
b) If the bulb has 5 % efficiency then the intensity is 0.05 times the intensity calculated above. Hence the electric field strength is
The magnetic field strength is