Oscillations & Waves
SHM, sound waves, Doppler effect, standing waves
Key Concepts
- SHM: restoring force F = −kx; acceleration proportional to and opposite to displacement
- Resonance: maximum amplitude when driving frequency = natural frequency
- Sound is a longitudinal mechanical wave; light is a transverse EM wave
- Standing waves: nodes (zero amplitude) and antinodes (maximum amplitude)
- Doppler effect: apparent frequency changes with relative motion of source/observer
Important Formulae
| Angular frequency (spring) | ω = √(k/m); T = 2π√(m/k) |
| Simple pendulum period | T = 2π√(L/g) |
| Wave speed | v = fλ |
| Speed of sound (air) | v = √(γP/ρ) ≈ 331 m/s at 0°C |
| Doppler formula | f' = f (v ± v_o) / (v ∓ v_s) |
| SHM energy | E = ½mω²A² |
Quick Tips
- In Doppler formula: upper signs when source/observer approach, lower signs when receding.
- Beats frequency = |f₁ − f₂|; used to tune musical instruments.
- For a pipe open at both ends: harmonics are n = 1, 2, 3…; closed at one end: only odd harmonics.
Sample Practice Questions
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In a transverse wave, particles vibrate:
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Answer: Perpendicular to direction of propagation
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The quality factor (Q-factor) in SHM indicates:
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Answer: Sharpness of resonance
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Frequency of second overtone in a closed pipe of length L (speed of sound v):
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Answer: 5v/4L
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Ultrasonic waves have frequency:
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Answer: Above 20 kHz
Practice Questions
Practice 20 randomly selected NEET questions on Oscillations & Waves. Answers are revealed after each question.
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What are the key concepts in Oscillations & Waves for NEET?
SHM: restoring force F = −kx; acceleration proportional to and opposite to displacement; Resonance: maximum amplitude when driving frequency = natural frequency; Sound is a longitudinal mechanical wave; light is a transverse EM wave; Standing waves: nodes (zero amplitude) and antinodes (maximum amplitude); Doppler effect: apparent frequency changes with relative motion of source/observer.
Which formulae are important for Oscillations & Waves in NEET?
Angular frequency (spring): ω = √(k/m); T = 2π√(m/k); Simple pendulum period: T = 2π√(L/g); Wave speed: v = fλ; Speed of sound (air): v = √(γP/ρ) ≈ 331 m/s at 0°C; Doppler formula: f' = f (v ± v_o) / (v ∓ v_s); SHM energy: E = ½mω²A².
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