Activity 10.7 Let us experiment to study how the frequency of sound changes. Class 9

Activity 10.7 Let us experiment to study how the frequency of sound changes. Class 9

Activity 10.7 Let us experiment (demonstrative activity)

Aim: To study how the frequency of sound changes with different muscial notes using a sound frequency mobile app.

Observation:

1. Open a mobile app that can generate sounds. Listen to sound of frequency 100 Hz. Increase the frequency upto 20000 Hz and then reduce thefrequency till 20 Hz.
2. Different musical notes produces different frequencies, as "Sa" has the lowest frequency among the set.
3. Voice generated and app-generated notes show similar frequency values for the same note.

Conclusion: Different musical notes have different frequencies. Musical notes follow a systematic pattern of frequency ratios.

Question 1.

If there are 10 density oscillations in 2 seconds at a given position, then find the frequency and time period of sound wave. Class 9

Answer:

Frequency = [latex]=\frac{\text { number of oscillation }}{\text { time taken }}[/latex]

= 10/2 = 5 Hz

v = [latex]\frac{1}{T}[/latex]; Time period is T = 1/5 = 0.2 s