Example 1 · level 1
A sound wave in air has frequency 500 Hz and wavelength 0.68 m. Find its speed (in m/s, correct to 2 decimal places).
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- v = 500 × 0.68 = 340 m/s.
Answer: 340
CLASS 9 SCIENCE · SOUND
Speed, frequency and wavelength of sound
v = fλ (speed = frequency × wavelength). Time period T = 1/f.
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Worked examples
Example 2 · level 2
Sound travels at 1500 m/s in water. Find the wavelength (in m) of a 500 Hz tone from a temple bell (correct to 3 decimal places).
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- λ = 1500 ÷ 500 = 3 m.
Answer: 3 m
Example 3 · level 3
A tuning fork vibrates at 800 Hz. Find the time period of the sound wave in milliseconds (ms).
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- T = 1/800 s = 0.00125 s = 1.25 ms.
Answer: 1.25 ms