Question

Question #931da

Answer 1

The standard for this type of problem is the universal wave equation, `v=f lamda`, except for this particular question there is a shortcut.

Explanation:

Bear with me, I will be brief:
Speed is distance over time, so time is distance over speed:

`t=d/v`

in the case of a wave, the distance travelled is the length of the wave, or the wavelength, `lamda`.
so

`t=lamda/v`

and from the universal wave equation, `v=f lamda`
so

`t=lamda/(f lamda)`
and
`t=cancel lamda/(f cancel lamda) = 1/f`

Which, if you stop to thing about it makes perfect sense, since the time for one wave to pass by is the period of the wave `T`, and

`T=1/f`

So the only value you actually need to solve this is the frequency!

Answer 2

The time taken for a wave to pass a point is the period, `T (s)`, which is simply the inverse of the frequency, `f (Hz = s^-1)`. In this case, `T=1/f = 1/300 = 0.00333 s`

Explanation:

Waves have three characteristics: velocity `v (ms^-1)`, wavelength `lambda (m)` and frequency `f (Hz)`.

These characteristics are related by the formula: `v=flambda`

The unit of frequency, hertz `Hz` is 'per second': number of waves passing a point each second, and is `s^-1` in SI units.

In this question, we want the inverse of the frequency. If 300 waves pass a point in 1 second, how many seconds does it take for 1 wave to pass the same point? The answer is `1/f=1/300=0.00333 s`.