The siren of a fire engine that is driving northward at 30.0 m/s emits a sound of frequency 2000 Hz. A truck in front of this fire engine is moving northward at 20.0 m/s. (a) What is the frequency of the siren's sound that the fire engine's driver hears reflected from the back of the truck? (b) What wavelength would this driver measure for these reflected sound waves?
Properties of sound
A sound wave is a mechanical wave (or mechanical vibration) that transit through media such as gas (air), liquid (water), and solid (wood).
Quality Of Sound
A sound or a sound wave is defined as the energy produced due to the vibrations of particles in a medium. When any medium produces a disturbance or vibrations, it causes a movement in the air particles which produces sound waves. Molecules in the air vibrate about a certain average position and create compressions and rarefactions. This is called pitch which is defined as the frequency of sound. The frequency is defined as the number of oscillations in pressure per second.
Categories of Sound Wave
People perceive sound in different ways, like a medico student takes sound as vibration produced by objects reaching the human eardrum. A physicist perceives sound as vibration produced by an object, which produces disturbances in nearby air molecules that travel further. Both of them describe it as vibration generated by an object, the difference is one talks about how it is received and other deals with how it travels and propagates across various mediums.
![1. The siren of a fire engine that is driving northward at 30.0 m/s emits a sound of
frequency 2000 Hz. A truck in front of this fire engine is moving northward at 20.0 m/s.
(a) What is the frequency of the siren's sound that the fire engine's driver hears reflected
from the back of the truck? (b) What wavelength would this driver measure for these
reflected sound waves?
2. A point charge is placed at each corner of a square with side length a. All charges have
magnitude q. Two of the charges are positive and two are negative (Fig. A1.2). What is
the direction of the net electric field at the center of the square due to the four charges,
and what is its magnitude in terms of q and a?](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Ff3144732-cd8e-4d15-8b5e-c18450259e48%2F03f8f05c-c3d6-4306-99c4-6f1b0a4d40b7%2Fbh83rml_processed.jpeg&w=3840&q=75)
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