# Hertz's Experiments (1 Viewer)

#### 1729

##### Active Member
How did Hertz measure the speed of radio waves? Different sources say different things however they all said the frequency of the wave was known due to the experimental setup:

1. He allowed radio waves to reach the receiver via two different paths: one direct and one after reflecting off a metallic surface. This produced an interference pattern near the receiver which was studied to find wavelength.

2. He reflected the radio waves with 90 degree incidence angle off a flat plate to produce a standing wave and then he moved the receiver along the wave and calculated half the wavelength as the distance between nodes or antinodes.

3. He used diffraction to produce a resulting waveform which was studied to find wavelength.

Which of these is correct? Why are there so many different versions?

#### sida1049

##### Well-Known Member
Experimental setups (1) and (2) are equivalent. They're describing the same thing but with slightly different words.

I'm not sure about (3); I can't verify it online, and it sounds incorrect.

#### 1729

##### Active Member
Experimental setups (1) and (2) are equivalent. They're describing the same thing but with slightly different words.

I'm not sure about (3); I can't verify it online, and it sounds incorrect.
How are 1 and 2 equivalent?

1:

2:

Also, does (1) produce a standing wave? Don't you need two waves of the same frequency interfering while travelling in opposite directions?

#### sida1049

##### Well-Known Member
How are 1 and 2 equivalent?

1: View attachment 34532

2: View attachment 34531

Also, does (1) produce a standing wave? Don't you need two waves of the same frequency interfering while travelling in opposite directions?
Ahh, I see the problem now; I visualised (2) as (1). When I did HSC physics, I was taught that Hertz's experimental setup was (1). And you're absolutely right; you do need two waves travelling in opposite directions to generate a standing wave.

It's entirely possible that (1) and (2) are experimental setups that Hertz constructed at some point, but I haven't dug far enough to check whether he actually did. I would recommend going with (1) to be safe.