Electromagnetic Waves: Class 12 Physics Q&A
4 free answers on Electromagnetic Waves (Physics) for Class 12 students, across CBSE, ICSE and State boards. Includes questions such as “What does 1/√(ε₀μ₀) signify?”, “How to calculate wavelength to frequency?”, “How does relativistic velocity addition work”.
Question & Answer
Questions
- PhysicsClass 12All
What does 1/√(ε₀μ₀) signify?
1/√(ε₀μ₀) equals the speed of light in vacuum (c ≈ 3 × 10⁸ m/s), where ε₀ is the permittivity of free space (8.854 × 10⁻¹² F/m) and μ₀ is the permeability of free space (4π × 10⁻⁷ H/m). This relationship demonstrates that the speed of electromagnetic waves emerges from fundamental properties of space itself. It's a cornerstone result from Maxwell's equations, showing how electricity and magnetism unify to produce electromagnetic
- PhysicsClass 12All
How to calculate wavelength to frequency?
To convert wavelength to frequency, rearrange the wave equation to f = v/λ. For electromagnetic waves, use f = c/λ where c = 3 × 10⁸ m/s. For example, if light has a wavelength of 500 nm (500 × 10⁻⁹ m), its frequency is f = (3 × 10⁸)/(500 × 10⁻⁹) = 6 × 10¹⁴ Hz. This calculation is essential in spectroscopy, telecommunications, and understanding electromagnetic radiation properties.
- PhysicsClass 12All
How does relativistic velocity addition work
Unlike classical physics, velocities don't simply add at high speeds. The relativistic formula is: v = (v₁ + v₂)/(1 + v₁v₂/c²) where c is the speed of light. Why this matters: Classical: If you throw a ball at 10 m/s from a train moving 20 m/s, ball speed = 30 m/s ✓ Relativistic: If spaceship A moves at 0.9c and fires a projectile at 0.9c, projectile speed ≠ 1.8c
- PhysicsClass 12All
Why can't anything travel faster than the speed of light?
According to Einstein's special relativity, as an object approaches the speed of light (c ≈ 299,792,458 m/s), its mass effectively increases, requiring infinite energy to reach light speed. The relativistic mass formula is: m = m₀/√(1 - v²/c²) What happens at high speeds: ● At 90% light speed, mass increases by 2.3 times ● At 99% light speed, mass increases by 7 times ● At 100% light speed, mass would be infinite (impossible) Insight: This is a fundamental law of physics