Doppler Effect

A train at rest emits sound waves with frequency f. The train moves away from you at speed v, and the speed of sound is c. Which of the following is the frequency of the sound waves received by a stationary observer?

• $f\left(\frac{c}{c-v}\right)$

• $f\left(\frac{c}{c+v}\right)$

• $f\left(\frac{c-v}{c}\right)$

• $f\left(\frac{c+v}{c}\right)$

A train at rest emits sound waves with frequency f. The train moves toward you at speed v, and the speed of sound is c. Which of the following is the frequency of the sound waves received by a stationary observer?

• $f\left(\frac{c}{c-v}\right)$

• $f\left(\frac{c}{c+v}\right)$

• $f\left(\frac{c-v}{c}\right)$

• $f\left(\frac{c+v}{c}\right)$

A stationary foghorn emits sound waves with frequency f. The speed of sound is c. If an airplane moving at speed v travels toward the foghorn, what frequency will a person in the airplane receive?

• $f\left(\frac{c}{c-v}\right)$

• $f\left(\frac{c}{c+v}\right)$

• $f\left(\frac{c-v}{c}\right)$

• $f\left(\frac{c+v}{c}\right)$

A stationary foghorn emits sound waves with frequency f. The speed of sound is c. If an airplane moving at speed v travels away from the foghorn, what frequency will a person in the airplane receive?

• $f\left(\frac{c}{c-v}\right)$

• $f\left(\frac{c}{c+v}\right)$

• $f\left(\frac{c-v}{c}\right)$

• $f\left(\frac{c+v}{c}\right)$

A galaxy emits a radio wave with a wavelength of  $\lambda$ . If the galaxy moves away from us at speed  $v$ , what wavelength we will observe on Earth? 

• We will receive a wavelength of  $\lambda+\Delta\lambda$ .

• We will receive a wavelength of  $\lambda-\Delta\lambda$ .

• We will receive a wavelength of  $\lambda$ .

• We will receive a wavelength of  $\Delta\lambda$ .

A galaxy emits a radio wave with a frequency of  $f$ . If the galaxy moves away from us at speed  $v$ , what frequency will we observe on Earth? 

• We will receive a frequency of  $f+\Delta f$ .

• We will receive a frequency of  $f-\Delta f$ .

• We will receive a frequency of  $f$ .

• We will receive a frequency of  $\Delta f$ .