1
\mathrm{f}=\frac{1}{\mathrm{T}}
2
\mathrm{v}=\mathrm{f}\mathrm{\lambda}
3
\text{Depth}=\frac{\mathrm{v}\mathrm{t}}{2}
4
\mathrm{h}=\frac{\mathrm{t}}{2}\sqrt{\mathrm{V}^{2}-\mathrm{v}^{2}}
5
\mathrm{T}=\frac{1}{\mathrm{f}}
FORMULA CHAPTER
Chapter 07 – Sound
ICSEClass 10Physics5 formulas
Revise ICSE Class 10 Chapter 07 Sound formulas for frequency, time period, wavelength, wave speed and echo calculations.
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Frequency from Time Period
\mathrm{f}=\frac{1}{\mathrm{T}}
SymbolMeaningUnit
fFrequencyHz
TTime periods
Worked example
Question: A wave has a time period of 0.25 s. Find its frequency.
Calculation: f = 1/T
⇒ f = 1/0.25
⇒ f = 4 Hz
Answer: The frequency is 4 Hz.
Wave Equation
\mathrm{v}=\mathrm{f}\mathrm{\lambda}
SymbolMeaningUnit
vwave speedm/s
ffrequencyHz
λwavelengthm
Worked example
Question: Using Wave Equation, solve the case where f = 500 Hz, wavelength = 0.68 m.
Calculation: Apply the Wave Equation formula.
Step 1: Substitute the stated values into the formula.
Step 2: v = 500 × 0.68.
Answer: v = 340 m/s.
Echo Depth Formula
\text{Depth}=\frac{\mathrm{v}\mathrm{t}}{2}
SymbolMeaningUnit
vSpeed of soundm/s
tEcho times
Worked example
Question: Using Echo Depth Formula, solve the case where v = 1500 m/s, t = 2 s.
Calculation: Apply the Echo Depth Formula formula.
Step 1: Substitute the stated values into the formula.
Step 2: Depth = 1500 × 2 / 2.
Answer: Depth = 1500 m.
Height of a Moving Aeroplane from Echo
\mathrm{h}=\frac{\mathrm{t}}{2}\sqrt{\mathrm{V}^{2}-\mathrm{v}^{2}}
SymbolMeaningUnit
hHeight of aeroplanem
tTime differences
VSpeed of sound in airm/s
vSpeed of aeroplanem/s
Worked example
Question: Using Height of a Moving Aeroplane from Echo, solve the case where v = 340 m/s, v = 100 m/s, t = 2 s.
Calculation: Apply the Height of a Moving Aeroplane from Echo formula.
Step 1: Substitute the stated values into the formula.
Step 2: h = 1 × √(340² − 100²).
Answer: h ≈ 325 m.
Time Period from Frequency
\mathrm{T}=\frac{1}{\mathrm{f}}
SymbolMeaningUnit
TTime periods
fFrequencyHz
Worked example
Question: Using Time Period from Frequency, solve the case where f = 5 Hz.
Calculation: Apply the Time Period from Frequency formula.
Step 1: Substitute the stated values into the formula.
Step 2: T = 1/5.
Answer: T = 0.2 s.