FariÃ±a grew up in Brooklyn, the daughter of two Spanish immigrants who spoke that language at home. At Monday's press conference, she told a story of a postcard that her father, who she said had a third-grade education and taught her about the importance of education, received in the mail from her school.
The Doppler effect is the apparent shift in wave frequency due to the movement of a wave source. The apparent frequency shifts upward when the wave source is approaching and downward when the wave source is retreating. The Doppler effect explains why we perceive a change in pitch of the sound of a passing siren.
Doppler Effect. You hear the high pitch of the siren of the approaching ambulance, and notice that its pitch drops suddenly as the ambulance passes you. That is called the Doppler effect. When a vehicle with a siren passes you, a noticeable drop in the pitch of the sound of the siren will be observed as the vehicle passes. This is an example of the Doppler effect. An approaching source moves closer during period of the sound wave so the effective wavelength is shortened, giving a higher pitch since the velocity of the wave is unchanged.