Consider a source of sound `S`, and an observer `P`. The source emits sound of frequency `N_(0)`. The frequency observed by `P` is found to be `N_(1)` if P approaches S at a speed v and S is stationary; `N_(2)` if S approaches P at a speed v and P is stationary and `N_(3)` if each of P and S has speed v/2 towards one another ​

Options

A. `N_(1) =N_(2) =N_(3)`
B. `N_(1) lt N_(2)`
C. `N_(3) lt N_(0)`
D. `N_(3)` lies between `N_(1)` and `N_(2)`

Explanation

To solve the problem step by step, we will use the Doppler effect equations for sound, which describe how the frequency of sound changes for an observer moving relative to a source of sound.

### Step 1: Understanding the Doppler Effect
The Doppler effect describes how the frequency of sound changes when the source or observer is moving. The formula for the observed frequency \( N \) when the source is stationary and the observer is moving towards the source is given by:

\[ N = N_0 \left( \frac{v + v_o}{v} \right) \]
...