Mnemonic 1: EM Spectrum Order (Increasing Frequency)
"Rich Men In Visible Uniforms eXude Glamour"
- Radio waves → Microwaves → Infrared → Visible → Ultraviolet → eX-rays → Gamma rays
- Frequency increases left to right
- Wavelength decreases left to right (since c = fλ, fixed c)
Mnemonic 2: Visible Spectrum (VIBGYOR)
"Violent Beasts In Greenland Yield Orange Rabbits"
- Violet (400 nm, highest frequency in visible)
- Indigo → Blue → Green → Yellow → Orange
- Red (700 nm, lowest frequency in visible)
- Violet = shortest λ, highest frequency; Red = longest λ, lowest frequency
Mnemonic 3: Applications
- "MOM" — Microwaves Ovens Magnetrons: Microwave ovens use magnetron to produce microwaves
- "SLUG" — avoid confusion: Sterilisation and LASIK = UV (not Gamma!); Gamma = cancer
- "X marks the BONE": X-rays → medical imaging → bones
- "IR is Infrared = heaR": IR produces heat → physiotherapy, night vision (warm objects)
- "GAMMA gets cancer": Gamma rays are used in cancer treatment (radiotherapy)
- "Radio DJs are LAZY (low frequency)": Radio waves have the lowest frequency
Mnemonic 4: Displacement Current
"MAX FIXED AMPS": Maxwell Fixed Ampere's law by adding displacement current.
- The "fix" = add ε_{0}(dΦ_E/dt) to conduction current
- Key: it's NOT real charge flow; it EQUALS conduction current in the wire; produces B field
Mnemonic 5: E–B Phase
"E and B are BEST FRIENDS": They walk together (in phase) — peaks, zeros, and troughs all at the same time. They stand back-to-back (perpendicular in space) but always move in sync (in phase in time).