The frequency of sound waves can be expressed in

Options

A. Hz only
B. cycles/second only
C. `s^(-1)` only
D. all the above

Answer

To solve the question regarding how the frequency of sound waves can be expressed, we will follow these steps:

### Step-by-Step Solution:

1. **Understanding Frequency**:
- Frequency is defined as the number of cycles of a wave that occur in one second. It is mathematically represented as:
\[ f = \frac{1}{T} \]
where \( f \) is the frequency and \( T \) is the time period (the duration of one complete cycle).

2. **Identifying Units of Time Period**:
- The unit of time period \( T \) is seconds (s). Therefore, when we express frequency, we can use the reciprocal of time period.

3. **Units of Frequency**:
- The unit of frequency is Hertz (Hz), which is equivalent to cycles per second. This means that if a wave completes one cycle in one second, its frequency is 1 Hz.

4. **Expressing Frequency in Different Forms**:
- Frequency can be expressed in various forms:
- **Hertz (Hz)**: This is the standard unit of frequency.
- **Cycles per second**: This is a direct interpretation of Hertz, as 1 Hz is equal to 1 cycle per second.
- **Second inverse (s⁻¹)**: This is another way to express frequency, indicating how many cycles occur in one second.

5. **Conclusion**:
- Since all the options provided (Hertz, cycles per second, and second inverse) are valid expressions for frequency, the correct answer to the question is:
- **All the above**.

### Final Answer:
The frequency of sound waves can be expressed in:
- **All the above** (Hertz, cycles per second, second inverse).

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