EM Waves chhota theory chapter hai — displacement current, EM spectrum aur wave properties. Yahan aapko is chapter ke sabse important formulas aur quick revision points free milte hain — NCERT/CBSE syllabus ke hisaab se, boards aur JEE/NEET dono ke liye.
Important Formulas & Concepts — Electromagnetic Waves
- Displacement current: I_d = ε₀·dφ_E/dt
- c = 1/√(μ₀ε₀) = 3 × 10⁸ m/s
- c = E₀/B₀
- EM wave mein E ⊥ B ⊥ propagation
- Energy density: u = ½ε₀E² + B²/2μ₀
- Intensity I = u_avg × c
- Momentum p = U/c; radiation pressure
- Spectrum (increasing λ): gamma → X-ray → UV → visible → IR → microwave → radio
Quick Revision Points
- EM waves ko medium nahi chahiye
- Spectrum order + uses rato: X-ray (bones), UV (sterilization), IR (remote), microwave (radar/oven)
- Maxwell ne displacement current se Ampere law fix kiya
- E aur B same phase mein oscillate karte hain
- Visible range: 400-700 nm
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FAQ
Ye chapter easy marks hai?
Haan — spectrum ke uses aur basic formulas se 3-4 marks pakke. PDF ka one-pager kaafi hai.
Displacement current kya hai?
Changing electric field se effective current — capacitor ke beech Ampere law isi se complete hota hai.
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