9.3 CHAPTER 9. DOPPLEREFFECT
- The Doppler Effect canbe observed in all typesof waves, including ultrasound,
light and radiowaves. - Sonography makes useof ultrasound and the Doppler Effect to determine the
direction of blood flow. - Light is emitted by stars. Due to the DopplerEffect, the frequency ofthis light
decreases and the startsappear red. This is called a red shift and meansthat the
stars are moving away from the Earth. This means that the Universe is expanding.
Chapter 9 End of Chapter Exercises
- Write a definition foreach of the following terms.
(a) Doppler Effect
(b) Red-shift
(c) Ultrasound - Explain how the Doppler Effect is used to determine the direction of
blood flow in veins. - The hooter of an approaching taxi has a frequency of 500 Hz. If the
taxi is travelling at 30 m·s−^1 and the speed of soundis 300 m·s−^1 ,
calculate the frequencyof sound that you hear when
(a) the taxi is approaching you.
(b) the taxi passed youand is driving away. - A truck approachesyou at an unknown speed. The sound of the
trucks engine has a frequency of 210 Hz, however you hear a fre-
quency of 220 Hz. Thespeed of sound is 340 m·s−^1.
(a) Calculate the speedof the truck.
(b) How will the soundchange as the truck passes you? Explain this
phenomenon in termsof the wavelength andfrequency of the
sound. - A police car is driving towards a fleeing suspect at 35 v m.s−^1 , where
v is the speed of sound. The frequency of the police car’s siren is
400 Hz. The suspect is running away at 68 v. What frequency does the
suspect hear? - (a) Why are ultrasound waves used in sonography and not sound
waves?
(b) Explain how the Doppler effect is used to determine the direction
of flow of blood in veins.
More practice video solutions or help at http://www.everythingscience.co.za
(1.) 01ui (2.) 01uj (3.) 01uk (4.) 01um (5.) 01un (6.) 01up