s by. The sound waves in front of the car arecondensed, while the trailing sound waves are longer and of a lower pitch. Light from anobject moving towards the Earth is shifted toward the blue end of the spectrum, where aslight from objects moving away is shifted toward the red end.The human ear cannot hear all possible frequencies. Very few people can hearany fewer than 16 Hz or any more than about 20 kHz (kilohertz--1 kHz equals 1,000 Hz).Music rarely makes use of this whole range of audible frequencies. The lowest note on apiano has a frequency of 27 Hz and the highest note a little more than 4 kHz. Frequency-modulation (FM) radio stations broadcast notes up to 15 kHz. These can be heard throughhi-fi receivers. The intensity of a sound has nothing to do with its pitch. A high tone can be eitherloud or soft, and so can a low tone. Intensity depends upon the strength, or amplitude, ofthe vibrations producing the sound. A piano string, for example, vibrates gently if the keyis struck softly. The string swings back and forth in a narrow arc, and the tone it sendsout is soft. If the key is struck forcefully, however, the string swings back and forth in awider arc. The stronger vibration then produces a louder tone. Redshift is a Doppler effect which states that if a galaxy is moving away, thespectral line of that galaxy observed will have a shift to the red end. The faster the galaxymoves, the more shift it has. If the galaxy is moving closer, the spectral line will show ablue shift. If the galaxy is not moving, there is no shift at all. However, as astronomersobserved, the more distance a galaxy is located from Earth, the more redshift it shows onthe spectrum. This means the further a galaxy is, the faster it moves. ...
