24.2 Production of Electromagnetic Waves

If an electromagnetic wave is described as having a frequency of 3 GHz, what are its period and wavelength (in a vacuum)?

1. 3.0 × 10⁹s, 10 cm
2. 3.3 × 10⁻¹⁰s, 10 cm
3. 3.3 × 10⁻¹⁰s, 10 m
4. 3.0 × 10⁹s, 10 m

A wave is travelling through a medium until it hits the end of the medium and there is nothing but vacuum beyond. What happens to a mechanical wave? Electromagnetic wave?

1. reflects backward, continues on
2. reflects backward, reflects backward
3. continues on, continues on
4. stops, continues on

Given the waveform in the figure(d), if $T \textrm{ } = \textrm{ } 3.0 \times 10^{- 9} \textrm{ } \text{s}$ and $E \textrm{ } = \textrm{ } 5.0 \times 10^{5} \textrm{ } \text{N}\textrm{ }/\textrm{ }\text{C}$, which of the following is the correct equation for the wave at the antenna?

1. $\left(\text{5} .\text{0} \times 10^{5} \textrm{ } \text{N}\textrm{ }/\textrm{ }\text{C}\right) \textrm{ } \text{sin} \textrm{ } \left(\text{2} \pi \textrm{ } \left(\text{3} .\text{0} \textrm{ } \times 10^{- 9} \textrm{ } \text{s}\right) t\right)$
2. $\left(\text{5} .\text{0} \times 10^{5} \textrm{ } \text{N}\textrm{ }/\textrm{ }\text{C}\right) \textrm{ } \text{sin} \textrm{ } \left(\frac{\text{2} \pi \textrm{ } t}{\left(\text{3} .\text{0} \textrm{ } \times 10^{- 9} \textrm{ } \text{s}\right)}\right)$
3. $\left(\text{5} .\text{0} \times 10^{5} \textrm{ } \text{N}\textrm{ }/\textrm{ }\text{C}\right) \textrm{ } \text{cos} \textrm{ } \left(\text{2} \pi \textrm{ } \left(\text{3} .\text{0} \textrm{ } \times 10^{- 9} \textrm{ } \text{s}\right) t\right)$
4. $\left(\text{5} .\text{0} \times 10^{5} \textrm{ } \text{N}\textrm{ }/\textrm{ }\text{C}\right) \textrm{ } \text{cos} \textrm{ } \left(\frac{\text{2} \pi \textrm{ } t}{\left(\text{3} .\text{0} \textrm{ } \times 10^{- 9} \textrm{ } \text{s}\right)}\right)$

In Heinrich Hertz’s spark gap experiment (the reference), how will the induced sparks in Loop 2 compare to those created in Loop 1?

1. Stronger
2. Weaker
3. Need to know the tuner settings to tell
4. Weaker, but how much depends on the tuner settings.

What is the maximum electric field strength in an electromagnetic wave that has a maximum magnetic field strength of $5 . \text{00} \times \text{10}^{- 4} \text{ T}$ (about 10 times the Earth’s)?