Aracecar is traveling around a track. under what circumstance would you hear the highest pitch? a) as the car is moving slowly toward you. b) as the car is moving quickly toward you. c) as the car is moving slowly away from you. d) as the car is moving quickly away from you.

Explanation:

The higher the frequency of the sound wave the higher the pitch. So, the sound with the highest frequency will have the highest pitch.

When the source of a sound (the car) has a relative motion to an observer (you) there is an apparent change in the frequency of the sound wave. This is known as the Doppler effect.

As the source of the sound is moving toward the observer, the sound waves will shorthen their wave length, so, since the inverse relation between the wave length and the frequency, the result is an apparent increase of the frequency of the sound.

The faster the source is moving toward you (the observer) the greater the effect (increase of the frequency) and so the higher the pitch. This is what the option B) describes: as the car is moving quickly toward you, you would hear the highest pitch.

The opposite happens when the source of the sound moves away from the observer: the pitch lowers.

The Doppler effect is also observed with the light waves: when the light source is moving toward the observer the apparent change in the frequency implies a blue shift, when the source is moving away of the observer the apparent increase of the frequency leads to a red shift.

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

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