Question

The siren on an ambulance is emitting a sound whose frequency is 2450 Hz. The speed of sound is 343 m/s. If the ambulance is stationary and you (the "observer") are sitting in a parked car, what are the wavelength and the frequency of the sound you hear?

Answer 1

Step-by-step explanation:

It is given that,

Frequency of the siren, f = 2450 Hz

The speed of sound, v = 343 m/s

Here, both ambulance and the observer is stationary. The observed frequency is calculated using Doppler's effect as :

`f'=(v+v_o)/(v-v_s)* f`

`v_o` is the velocity of observer

`v_s` is the velocity of source

v is the speed of sound wave

Here,
`v_o=v_s=0`

So, f' = f

f' = 2450 Hz

Wavelength,
`\lambda'=(v)/(f')`

`\lambda'=(343\ m/s)/(2450\ Hz)`

`\lambda'=0.14\ m`

So, the frequency and wavelength of the observed sound is 2450 Hz and 0.14 meters. Hence, this is the required solution.

Answer 2

The wavelength is 0.14 m

Step-by-step explanation:

Given that,

Frequency = 2450 Hz

Speed of sound = 343 m/s

We need to calculate the wavelength

Using formula of wavelength

`v=  f\lambda`

Where, v = speed of sound

f = frequency

Put the value into the formula

`\lambda=(v)/(f)`

`\lambda=(343)/(2450)`

`\lambda=0.14\ m`

Hence, The wavelength is 0.14 m