a sound wave is produced fron a source ans an echo is heard t seconds afterwards. If d is the distance of the reflecting surface from the source, v the spee...

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When a sound wave is produced from a source, it travels through a medium (such as air) until it reaches a reflecting surface (such as a wall). At the reflecting surface, the sound wave bounces off and returns back towards the source, producing an echo. Let's assume that the time interval between the production of the sound wave and the reception of its echo is t seconds. The speed of sound in the medium is represented by v, the wavelength of the sound wave is represented by λ, and the period of the sound wave is represented by T. We want to find the distance (d) between the source and the reflecting surface. To do this, we can use the formula: d = vt/2 This formula relates the distance (d) to the speed (v) of the sound wave and the time (t) it takes for the echo to be heard. We can also express the speed (v) of the sound wave in terms of its wavelength (λ) and period (T): v = λ/T Substituting this expression for v into the first formula, we get: d = λt/2T Therefore, the answer is (b) d = \(\frac{\lambda t}{2T}\).