This lesson explores the wave and particle nature of electromagnetic radiation, the electromagnetic spectrum, and key equations that describe wave behavior.

1. Core Concepts (Short Notes)

2.1 What Is Electromagnetic Radiation?

Electromagnetic radiation (EMR) is a form of energy that travels through space as oscillating electric and magnetic fields. It can travel through a vacuum (unlike sound).

Examples include visible light, microwaves, X-rays, and gamma rays.

2.2 Wave-Particle Duality

Small particles like electrons behave as both waves and particles.

• Wave nature: diffraction and interference.

• Particle nature: photons and quantized energy.

Proposed by Louis de Broglie.

2.3 De Broglie Equation

Every moving particle has a wavelength: λ = h / (mv) Where h = Planck's constant.

2.4 Wave Properties

• Wavelength (λ): distance between peaks.

• Frequency (ν): waves per second.

• Speed of light (c): 3.0 × 10⁸ m/s.

Relationship: c = λν

2.5 Photon Energy

E = hν

High frequency → high energy.

2.6 Electromagnetic Spectrum

Increasing frequency order: Radio → Microwave → Infrared → Visible → UV → X-rays → Gamma

Visible range: 400–700 nm.

2. Key Formulas to Memorize

• c = λν

• E = hν

• E = hc / λ

• λ = h / (mv)

3. Tips & Tricks for Exams

• High frequency = dangerous radiation (UV, X-ray, gamma).

• Convert nm → m before calculations.

• Long wavelength = low energy.

• Visualize EM spectrum left to right: Radio → Gamma.

• Know visible colours: VIBGYOR (700 nm → 400 nm).

4. Important Points to Remember

• EM waves do not need a medium.

• All EM waves travel at the same speed in vacuum.

• Energy is quantized.

EM spectrum spans a huge range of wavelengths.