Hertz Experiment regarding EM Waves Flashcards
(8 cards)
How did Hertz produce radio waves in his experiment?
By allowing high voltage sparks to jump across a gap of air, generating radio waves.
What is a dipole receiver, and what does it detect?
A dipole receiver consists of a second set of parallel charged plates, and it detects the electric field of the radio waves.
What type of receiver detects the magnetic field of radio waves, and how does it work?
A loop of wire with a small gap detects the magnetic field. As the magnetic field alternates, it changes the magnetic flux through the loop, inducing a potential difference that can cause a spark across the gap.
What happens when a metal sheet is placed in front of the transmitter?
The radio waves are reflected back, causing interference with the incoming waves and forming stationary waves.
How can stationary waves be used to measure the wavelength of radio waves?
By detecting the distance between adjacent nodes (points of no displacement) in the stationary wave pattern using one of the detectors.
How did Hertz determine the speed of radio waves?
He measured the wavelength from the stationary wave pattern and used the known frequency to calculate speed using v=fλ. The result matched Maxwell’s predicted speed of EM waves.
What did Hertz observe when he rotated the detector 90° about the axis between transmitter and receiver?
The detected signal changed from a maximum to zero, confirming that the radio waves were polarised.
Why does signal strength vary when the detector is rotated in Hertz’s experiment?
Because at the maximum signal, the plane of the detector is perpendicular to the field oscillations, while after 90° rotation, it becomes parallel, detecting no signal — showing polarisation.
