Question

two boys have made a cup and string device to try to communicate. the sound wave from the voice of the boy on the right will have to travel through the cup, the match stick holding the string, the thread and the other cup and match stick until it reaches the ear of the boy on the left. each of these parts has different properties. which statement is true? (1 point) ○ the frequency remains constant. ○ the frequency changes, while the wavelength and speed of the wave remain the same. ○ the period changes, while the wavelength and the speed of the wave remain the same. ○ the period and the speed of the wave change proportionally.

Explanation:

To solve this, we recall the properties of sound waves when they travel through different media. The frequency of a sound wave is determined by the source (the boy's voice here) and does not change when the wave travels through different media (cup, string, etc.). The speed of sound depends on the medium's properties (like elasticity, density), so speed changes. Wavelength is related to speed and frequency by \(v = f\lambda\) (where \(v\) is speed, \(f\) is frequency, \(\lambda\) is wavelength). Since \(f\) is constant and \(v\) changes, \(\lambda\) also changes.

• For the first option: Frequency is determined by the source, so it remains constant as the wave moves through different parts (media) of the cup - string device. This matches our understanding.
• Second option: Frequency doesn't change, and speed (and thus wavelength) changes, so this is incorrect.
• Third option: Period is \(T=\frac{1}{f}\), so if \(f\) is constant, period is constant. Also, speed changes, so this is wrong.
• Fourth option: Period is constant (since \(f\) is constant), so period and speed can't change proportionally. This is incorrect.

Answer:

The frequency remains constant.