In 1864, James Clerk Maxwell published a theory that included an equation for the speed of electromagnetic waves in a vacuum - AQA - A-Level Physics - Question 2 - 2021 - Paper 7

In this experiment, the oscillating current in the transmitter (T) generates alternating electric and magnetic fields, as described by Maxwell's theory. These fields propagate through space as electromagnetic waves. The vertical metal rods in T act as an aerial that radiates these waves.

When the waves approach the conducting loop aerial (D), they induce an electromotive force (emf) due to the change in the magnetic field around the loop. This induced emf is a result of Faraday's law of electromagnetic induction, which states that a changing magnetic field within a closed loop creates an emf.

Thus, the interaction between the oscillating fields generated by the transmitter and the conducting loop detector illustrates the principles laid out in Maxwell's electromagnetic theory.

To determine if the arrangement can measure the speed of electromagnetic waves, we can analyze the frequency and distance involved. The frequency of the transmitter is given as 75 MHz, which is equivalent to:

$\text{Frequency (f)} = 75 \times 10^6 \text{ Hz}$

Using the wave equation, we know:

$v = f \times \lambda$

where ( v ) is the speed of the wave, and ( \lambda ) is the wavelength. The distance between the transmitter and reflector is given as 12 m. In stationary wave patterns, nodes occur at fixed points between the transmitter and the reflector, thus allowing the measurement of wavelength and ultimately frequency.

Using the transmitter's frequency to calculate the wavelength:

$\lambda = \frac{v}{f} = \frac{12 ext{ m}}{n}$

where n is the number of wavelengths fitting in the 12 m distance. This setup indeed allows for the measurement of the speed of electromagnetic waves as suggested by Maxwell's equation.