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Complete Mechanical Waves objective questions from basic to toughest JEE Advanced level.
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🌊 Waves – JEE Advanced Objective Library
Complete Mechanical Waves objective questions from basic to toughest JEE Advanced level.
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Central hub covering all Physics chapters with structured IIT-level preparation.
👉 Open Physics Master Library🏫 Learning Resource Hub
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🌊 Waves – JEE Advanced Objective Library
Complete Mechanical Waves objective questions from basic to toughest JEE Advanced level.
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Central hub covering all Physics chapters with structured IIT-level preparation.
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👉 Join WhatsApp Channel🌊 WAVES (Mechanical Waves)
Stage 2 – Page 10 : Doppler Effect with Wind (Advanced Level)
1️⃣ Why Wind Matters in Doppler Effect?
In real situations, air (medium) may move with velocity u (wind speed). Since sound travels relative to the medium, wind changes the effective speed of sound.
✔ Doppler effect depends on relative velocity with respect to medium, not ground.
2️⃣ Speed of Sound with Wind
- Sound speed in still air = v
- With wind in same direction → v + u
- With wind opposite direction → v − u
3️⃣ General Doppler Formula with Wind
f' = f × ( v ± vo ± u ) / ( v ∓ vs ± u )
Signs depend on direction of motion relative to wind.
4️⃣ Special Case: Observer & Source Stationary, Wind Present
Even if both observer and source are stationary (w.r.t ground), no Doppler effect occurs.
Wind changes wave speed, not frequency.
5️⃣ Relative Velocity Method (BEST JEE TRICK)
Always shift to medium frame.
- Velocity of source w.r.t medium = vs − u
- Velocity of observer w.r.t medium = vo − u
✔ Use standard Doppler formula after converting velocities.
6️⃣ Advanced JEE Numerical
A source emits sound of frequency 1000 Hz. Wind blows from source to observer at 10 m/s. Speed of sound = 330 m/s. Source is stationary, observer moves towards source at 20 m/s. Find observed frequency.
Solution:
Effective sound speed = 330 + 10 = 340 m/s
f' = 1000 × (340 + 20) / 340 = 1058.8 Hz
7️⃣ Doppler Effect in Echo & Reflection
- Double Doppler shift occurs
- First shift at reflecting surface
- Second shift when reflected wave reaches observer
f'' = f × ( v + vo ) / ( v − vs ) × ( v + vo ) / ( v − vs )
8️⃣ IIT-JEE Traps
- Using ground frame instead of medium frame
- Wrong wind direction assumption
- Mixing wind speed with observer speed
- Forgetting double Doppler in echo
9️⃣ Conceptual Questions
- Can wind alone cause Doppler effect?
- Why frequency remains same in stationary cases?
- What happens if wind direction reverses?
🎯 Final Takeaway
✔ Always convert to medium frame ✔ Wind changes speed, not frequency ✔ Relative velocity method is safest
Stage 2 – Page 10 Completed Successfully ✅
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