From graph of sound wave propagating in steel, find its wavelength. Class 9

From graph of sound wave propagating in steel, find its wavelength. Class 9

Question 1.

From graph of sound wave propagating in steel, find its wavelength. Calculate its frequency and time period if speed of sound in steel is 5000 m/s. Class 9

Answer:

From the graph, wavelength = 50 m

Speed of wave is u = v × λ

Frequency, v = 5000/50 = 100 Hz

v = [latex]\frac{1}{T}[/latex]; T = 1/100 = 0.01 s

Question 2.

Human hearing spans 20 Hz to 20 kHz. What are corresponding wavelengths in air for these two frequencies? Speed of sound in air is 340 m/s. Class 9

Answer:

u = v × λ

For v = 20 Hz, λ = 340/20 = 17 m

For v = 20 kHz = 20000 Hz, λ = 340/20000 = 0.017 m

Question 3.

During a thunderstorm, lightning flash is seen before thunder is heard. If time delay between seeing the lightning flash and hearing the thunder is 5 s , find the distance to lightning flash. Speed of sound in air is 340 m/s. Class 9

Answer:

Distance = speed × time = 340 × 5 = 1700 m