Table 1 gives results from a field test on a dry lakebed. A researcher stood 90.0 m from a rock face and made a short sound using two wooden blocks. A micro...
Question 1 Report
Table 1 gives results from a field test on a dry lakebed. A researcher stood 90.0 m from a rock face and made a short sound using two wooden blocks. A microphone connected to an oscilloscope recorded the time until the echo returned. The sound waves travelled to the rock face and back, so their total distance was 180.0 m. Fig. 1 shows the arrangement. The temperature of the air was changed by carrying out the test at different times of day.
| air temperature / °C | echo time / s |
|---|---|
| -5 | 0.545 |
| 5 | 0.529 |
| 15 | 0.514 |
| 25 | 0.500 |
(a) Calculate the speed of sound when the air temperature was 15 °C. [3]
(b) Describe the relationship between air temperature and the speed of sound shown by Table 1. [2]
(c) Explain why increasing the temperature makes sound travel faster through air. [1]
Answer Details
(a) The sound travels to the rock face and back, so its distance is:
\[2\times90.0=180.0\text{ m}\]
\[v=\frac{d}{t}=\frac{180.0}{0.514}=350\text{ m s}^{-1}\]
The speed of sound at \(15^\circ\text{C}\) is \(350\text{ m s}^{-1}\). [3]
(b) As air temperature increases, the echo time decreases. Since the total distance is unchanged, this means the speed of sound increases as temperature increases. [2]
(c) At a higher temperature, air particles have more kinetic energy and move faster. They pass vibrations between particles more quickly, so sound travels faster. [1]
Download The App On Google Playstore
Everything you need to excel in your exams
