According to the doppler effect, the sound of a police car siren is and pitched as it approaches the observer.

On the basis of the Doppler effect, the sound of a police car siren is louder and higher pitched as it move towards the observer.

Explanation:

Whenever the police car with a siren moves towards an individual, the frequency of the siren will increase and the reverse happens when the police car moves away from the person. The individual can listen to the sound of the siren louder and clearer when the car approaches the individual, as the sound is highly pitched when it moves towards the observer. This phenomenon is known as the Doppler effect.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

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