Wave Equation

Following NCERT Class 12, Chapter 8 (Electromagnetic Waves), every electromagnetic wave in vacuum satisfies the relation c = fλ, where c is the speed of light, f the frequency, and λ the wavelength. The wave carries energy through oscillating electric and magnetic fields and does not need a medium, which is why it can be transmitted freely inside the oven cavity. Because the speed is fixed, frequency and wavelength are inversely proportional, so a short centimetre-scale wavelength must correspond to a high gigahertz-scale frequency. Here λ = 12 cm = 0.12 m and c = 3 × 10⁸ m/s. Rearranging gives f = c/λ = (3 × 10⁸)/(0.12) = 2.5 × 10⁹ Hz, which lies in the microwave region and matches typical oven frequencies near 2.45 GHz, chosen because water molecules absorb such radiation efficiently. The value 3.6 × 10⁷ Hz is incorrect because it wrongly multiplies wavelength and speed instead of dividing. The value 2.5 × 10¹⁰ Hz results from using λ = 1.2 cm, a decimal-place error. The value 3.6 × 10⁹ Hz comes from multiplying rather than dividing with the wrong power of ten. A magnitude check confirms gigahertz-scale frequencies for centimetre-scale microwaves, so 2.5 × 10⁹ Hz is consistent.