Electromagnetic Waves (EM Waves)

🏠 Home Current Electricity Magnetism and matter

📘 Theory

• EM waves are produced by accelerating charges.
• They do not need any medium → can travel in vacuum.
• Speed of EM waves = c = 3 × 10⁸ m/s
• Electric field (E) ⟂ Magnetic field (B) ⟂ Direction of wave
• They are transverse waves.

⚡ Important Formulas

• c = 1 / √(μ₀ε₀)
• E = cB
• Energy density = (ε₀E²)/2
• Wave speed: v = fλ

🌈 EM Spectrum (Order)

Radio → Microwave → Infrared → Visible → UV → X-rays → Gamma rays

🧠 Tricks

• Memory Trick: "Raging Martians Invaded Venus Using X-ray Guns"
• Higher frequency → Higher energy
• Gamma rays have maximum energy

🔥 JEE PYQs

Q1: Speed of EM wave in vacuum is?

Ans: 3 × 10⁸ m/s

Q2: Relation between E and B?

Ans: E = cB

Q3: Which has highest frequency?

Ans: Gamma rays

Q4: Nature of EM waves?

Ans: Transverse

💡 Advanced Level

Q: If electric field is 300 V/m, find magnetic field.

Solution: B = E/c = 300 / (3×10⁸) = 10⁻⁶ T

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