Question

Week 12.)

1.) Assume the helium-neon lasers commonly used in student physics laboratories have power outputs of 0.250 mW. Find the peak magnetic field strength.

2.) An LC circuit with a 5.00-pF capacitor oscillates in such a manner as to radiate at a wavelength of 3.30 m. What inductance is in series with the capacitor? Record your answer in milliHenries.

6.13x10^11 for 2 is incorrect as well as 6.13x10^-7

Answer 1

Question 1

The formula for peak magnetic field strength from intensity is

However, to use this formula, we need to find the intensity, which requires us to know the area. The most common lasers project onto an area with diameter .

Now, we substitute this into our first equation.

Question 2

The frequency of oscillation is given by

We know that this frequency occurs at the resonant frequency of the LC circuit.

Substituting our values, we get