two piano keys are stuck simultaneously. the notes emitted by them have a frequencies 250 Hz and 253 Hz. the number of Beats heard per second is

Options

A. 1
B. 2
C. 3
D. 4

Answer

To solve the problem of finding the number of beats heard per second when two piano keys emit notes at frequencies of 250 Hz and 253 Hz, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Frequencies**:
- Let \( f_1 = 250 \, \text{Hz} \) (frequency of the first piano key).
- Let \( f_2 = 253 \, \text{Hz} \) (frequency of the second piano key).

2. **Calculate the Difference in Frequencies**:
- The number of beats per second is given by the absolute difference between the two frequencies.
- This can be calculated using the formula:
\[ \text{Beats per second} = |f_2 - f_1| \]

3. **Substitute the Values**:
- Substitute the values of \( f_1 \) and \( f_2 \):
\[ \text{Beats per second} = |253 \, \text{Hz} - 250 \, \text{Hz}| \]

4. **Perform the Calculation**:
- Calculate the difference:
\[ \text{Beats per second} = |3 \, \text{Hz}| = 3 \, \text{Hz} \]

5. **Conclusion**:
- Therefore, the number of beats heard per second is \( 3 \).

### Final Answer:
The number of beats heard per second is **3 beats per second**.

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