Frequency heard

by observer $($motorcycle$)$

$Hz$

Frequency

of source $($car$)$

$1000$

Part $1$ of $6-$ Stationary Source, Moving Observer

Seldon sets the car speed to $0\frac{m}{s}$ and the motorcycle speed to positive $10\frac{m}{s}.$ He clicks "run" and asks Krishna to observe what happens. How does Krishna describe what happens?

"The motorcycle moves toward the car $($the source of the sound$),$ and the observed frequency is greater than the source frequency. After the motorcycle passes the car, the observed frequency is again greater than the source frequency."

"The motorcycle moves toward the car $($the source of the sound$),$ and the observed frequency is less than the source frequency. After the motorcycle passes the car, the observed frequency is again less than the source frequency."

"The motorcycle moves toward the car $($the source of the sound$),$ and the observed frequency is greater than the source frequency. After the motorcycle passes the car, the observed frequency becomes less than the source frequency."

"The motorcycle moves toward the car $($the source of the sound$),$ and the observed frequency is less than the source frequency. After the motorcycle passes the car, the observed frequency becomes greater than the source frequency."