EM Waves & LASER — A/L Physics

What must I remember about EM Waves & LASER?

• Electromagnetic Spectrum: Continuous range of transverse electromagnetic waves in increasing frequency (decreasing wavelength): Radio, Microwave, Infrared, Visible (400-700 nm), Ultraviolet, X-ray, Gamma rays; all travel at speed c = 1 / √(μ0 ε0) ≈ 3 × 10⁸ m/s in vacuum.
• Electromagnetic Wave Nature: Mutually perpendicular electric (E) and magnetic (B) field vectors oscillating in phase, both perpendicular to the direction of propagation (E × B direction); E/B = c.
• LASER Acronym & Principles: Light Amplification by Stimulated Emission of Radiation; Key conditions: Population Inversion (metastable state holds more atoms than ground state), Pumping (energy injection), Stimulated Emission (incident photon triggers transition of identical photon).
• Characteristics of LASER Radiation: Highly Monochromatic (extremely narrow spectral linewidth), Highly Coherent (spatial and temporal phase locked), Highly Directional (minimal beam divergence), High Intensity.

Test yourself (1 minute)

1. Spontaneous vs Stimulated Emission

   Spontaneous emission emits photons randomly in arbitrary direction and phase (incoherent, e.g., incandescent bulbs); Stimulated emission produces photons with identical frequency, phase, direction, and polarization as trigger photon.

2. Energy of Photon

   E = h f = (h c) / λ where Planck's constant h = 6.626 × 10⁻³⁴ J·s; 1 eV = 1.602 × 10⁻¹⁹ J.

3. Optical Resonator Cavity

   Consists of one fully reflecting mirror and one partially transmitting mirror; provides positive optical feedback to sustain laser oscillations.

Practise EM Waves & LASER questions today

Source: NIE G.C.E. (A/L) Physics Resource Book - Unit 3: Waves & Modern Optics

What should I study first?

What comes next?

Next in the syllabus

Where does EM Waves & LASER fit in the syllabus?

Unit 3.7 · Year 1 · Term 2