In ECET 2026 Physics, Sound Waves are one of the most repeated topics. Questions appear almost every year on wave properties, formulas, and real-life applications. If you practice carefully, you can easily score 2–3 direct marks.
⚙️ Concept Notes – Sound Waves
- Sound Wave: A mechanical, longitudinal wave that propagates through a medium (solid, liquid, or gas) by compressions and rarefactions.
- Nature: Cannot travel in vacuum, requires a medium.
- Speed of Sound depends on medium’s density and elasticity.
Key Properties of Sound Waves:
- Wavelength (λ)
- Distance between two consecutive compressions or rarefactions.
Frequency (f)
- Number of oscillations per second. Unit = Hz.
Time Period (T)
- Time for one oscillation.
Wave Velocity (v)
Amplitude (A)
- Maximum displacement of particles from mean position. Determines loudness.
Intensity (I)
- Energy transmitted per unit area per unit time.
- Pitch – depends on frequency.
- Loudness – depends on amplitude.
- Quality/Timbre – depends on waveform (distinguishes same note from different instruments).
🌍 Real-Life Examples
- Echo: Reflection of sound from a surface (e.g., mountains, buildings).
- Sonar: Uses sound waves for underwater object detection.
- Medical Ultrasound: High-frequency sound used in imaging.
- Musical Instruments: Different sounds due to different frequencies and harmonics.
🔟 10 Expected MCQs – ECET 2026
Q1. Sound waves are:
A) Longitudinal
B) Transverse
C) Both
D) Electromagnetic
Q2. Unit of frequency is:
A) s
B) Hz
C) m
D) N
Q3. Velocity of sound in air at 20°C is approximately:
A) 150 m/s
B) 330 m/s
C) 500 m/s
D) 1000 m/s
Q4. Relation between frequency and time period is:
A) f = 1/T
B) f = T
C) f = T²
D) None
Q5. Which property decides the loudness of sound?
A) Frequency
B) Amplitude
C) Wavelength
D) Velocity
Q6. Intensity of sound is proportional to:
A) A
B) A²
C) 1/A
D) f × A
Q7. Quality of sound is determined by:
A) Wavelength
B) Waveform
C) Frequency
D) Velocity
Q8. Echo is due to:
A) Refraction
B) Diffraction
C) Reflection
D) Interference
Q9. If frequency = 500 Hz and velocity = 340 m/s, wavelength is:
A) 0.68 m
B) 6.8 m
C) 68 m
D) 0.034 m
Q10. Sound cannot travel through:
A) Solids
B) Liquids
C) Gases
D) Vacuum
✅ Answer Key
| Q.No | Answer |
|---|---|
| Q1 | A |
| Q2 | B |
| Q3 | B |
| Q4 | A |
| Q5 | B |
| Q6 | B |
| Q7 | B |
| Q8 | C |
| Q9 | A |
| Q10 | D |
🧠 Explanations
- Q1 → A: Sound waves are longitudinal in nature.
- Q2 → B: Frequency is measured in Hertz (Hz).
- Q3 → B: Speed of sound in air ≈ 330 m/s at room temp.
- Q4 → A: f = 1/T.
- Q5 → B: Loudness depends on amplitude.
- Q6 → B: Intensity ∝ A².
- Q7 → B: Quality depends on waveform.
- Q8 → C: Echo occurs due to reflection.
- Q9 → A: λ = v/f = 340/500 = 0.68 m.
- Q10 → D: Sound needs a medium, cannot travel in vacuum.
🎯 Why This Practice Matters
Sound waves are a scoring topic in Physics. Most questions are direct from formulas or properties. By mastering these, you can ensure 2+ marks in ECET Physics.
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