Detecting electromagnetic radiation
“Outside our consciousness there lies the cold and alien world of actual things. Between the two stretches the narrow borderland of the senses. No communication between the two worlds is possible excepting across the narrow strip. For a proper understanding of ourselves and of the world, it is of the highest importance that this borderland should be thoroughly explored.”
Heinrich Hertz’ Keynote Address at the Imperial Palace, Berlin, August, 1891
During the 1880s scientists from all over the world attempted to create an experiment that would prove Maxwell’s theory and allow one to detect electromagnetic radiation. According to Maxwell’s equations, a movement of charges causes an electric field. A changing magnetic field can cause an electric field and a changing electric field can cause a magnetic field. It wasn’t until 1886 when Hertz successfully put together an experiment that allowed him to detect electromagnetic waves and confirmed Maxwell’s theory.
Using an induction coil as a transmitter Hertz produced a current that traveled back and forth generating magnetic waves. As the waves propagated away from the apparatus the magnetic field changed which produced an EMF (induced current) detected on the metal loop located a few feet away. The EMF was detected by a spark that was produced in the spark gap of the loop (as seen above).
This experiment was the first successful attempt to prove Maxwell’s theory. The alternating current flowing between in the transmitter generated a changing electric field. The changing electric field created a changing magnetic field. As the electromagnetic waves traveled away from the transmitter towards the receiver an EMF was produced. This was seen through the spark that was produced on the receiver.
Realizing he was reaching a breakthrough, Hertz began more experiments on electromagnetic waves and discovered the velocity of the waves to be the speed of light.
Further study showed that electromagnetic waves exhibited similar characteristics as light waves. Electromagnetic waves have the ability to reflect, refract, and interfere. They have the ability to be focused, diffracted, and polarized. He published his findings in 1887 and in 1888 published another paper detailing his experimentations.
From then on the electromagnetic waves he discovered came to be known as Hertzian Waves. Nowadays we called Hertzian Waves “radio waves.”