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Sound wave frequency is the number of sound waves that pass a certain point in one second. It is measured in Hertz (Hz). In this exercise, the sound source emits waves at a frequency of 1200 Hz. This frequency will change depending on the relative motion of the source and the observer due to the Doppler Effect. Understanding the initial frequency is crucial as it will help us determine the apparent frequency at the reflecting surface. To summarize: frequency measures how often the sound waves occur, and in this problem, it starts at 1200 Hz.

Relative motion is the motion of an object as seen from another object. In the context of the Doppler Effect, relative motion between the sound source and the observer (or reflector) affects the frequency and wavelength of the sound waves detected. In this problem, the source A is moving towards the reflecting surface B at 29.9 m/s, and the reflecting surface B is moving towards the source at 65.8 m/s. The relative speed between these two objects is significant because it determines how the sound waves are perceived. Essentially, the effective speed is the sum of their individual speeds when moving towards each other.

Wavelength is the distance between successive crests of a wave. It is inversely proportional to frequency, meaning that as frequency increases, wavelength decreases and vice versa. To calculate the wavelength of the sound waves as heard by the reflecting surface, we use the formula: \[ \lambda = \frac{v}{f} \] where \( v \) is the speed of sound, and \( f \) is the frequency at any given point. For instance, if the apparent frequency at the reflecting surface has been calculated, we can substitute it in place of \( f \) and use \( 329 \ \text{m/s} \) for the speed of sound to find the wavelength at that point.

The Doppler Effect describes how the frequency of a wave changes for an observer moving relative to the source of the wave. The general formula used for sound waves when both the source and the observer are moving is: \[ f' = f \frac{v + v_o}{v - v_s} \] where \( f' \) is the observed frequency, \( f \) is the emitted frequency, \( v \) is the velocity of sound, \( v_o \) is the velocity of the observer, and \( v_s \) is the velocity of the source. This formula is key to solving problems involving the Doppler Effect as it allows us to calculate the frequency changes due to relative motion. By carefully identifying the velocities of the source and observer/reflector, we can apply this formula to determine the apparent frequency at different points during the motion.

The velocity of sound in a given medium (like air) is the speed at which sound waves travel through that medium. In this exercise, the speed of sound is given as 329 m/s. This value is crucial in both the Doppler Effect formula and the wavelength calculation. The velocity of sound is affected by factors like temperature, humidity, and the medium itself. In most physics problems, a standard value is used unless otherwise specified. For our problem, knowing the velocity of sound allows us to determine how the relative motion between the source and the reflector impacts the frequency and wavelength of the sound waves detected.