# Homework Help: Goniometers and Standing Waves

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1. Sep 23, 2015

### Mnemonic

1. The problem statement, all variables and given/known data
Initially your receiver is positioned at a distance of 8.4 cm from the goniometer and recording a maximum intensity. You move it through 10 minimums in the intensity and then stop at the next maximum intensity. The receiver is now a distance of 27.3 cm from the goniometer.

What is the wavelength of the signal you have measured?

2. Relevant equations
ƛ/2=Distance between two maximums

3. The attempt at a solution
ƛ=2(27.3-8.4)cm
=37.8cm

It's that simple right?
I keep getting the wrong answer with this. What am I missing?

2. Sep 24, 2015

### haruspex

You are not taking into account that it was moved through many minima and maxima. You have calculated as though it was moved to the very next maximum.

3. Sep 24, 2015

### Mnemonic

The wording in the question confused me. So you are saying that between each of the 10 minimums there was a maximum as well?

4. Sep 24, 2015

### haruspex

That's the usual arrangement.

5. Sep 24, 2015

### Mnemonic

SO there are 5 complete wavelengths.

Therefore ƛ=(27.3-8.4)/5 cm

6. Sep 24, 2015

### haruspex

That looks better.