Physic as level waves

A max occurs when the difference in path length is a whole number of wavelengths

There are two frequencies. How then do we calculate the speed?


Posted from TSR Mobile

The first frequency (1050Hz) will correspond to a certain number of whole wavelengths fitting in the 1.8m path difference.
The second frequency will correspond to the previous number of whole waves plus one more.

If that is so, by my calculation, for the frequency 1050Hz, the wavelength is 1.8/3 and for the frequency 1400Hz, the wavelength is 1.8/4. The speed will be 630ms-1.
Is this the way?


Posted from TSR Mobile

That's the right answer. With multiple choice it's getting there that's important.
How did you get the numbers 3 and 4, by the way?
There are indeed 3 full waves in the first case and 4 in the second.
Was it a bit of guess work? Trial and error?

The full treatment would involve saying that for the 1st frequency

1.8 = nλ₁

and for the 2nd frequency

1.8 = (n+1)λ₂

and λ=v/f

Initially, it was guess work, then there was this solution....


Posted from TSR Mobile

Yes you get n=3 and from that the value of v