9702 · 7.4
Electromagnetic spectrum — FAQ
Frequently asked questions for 9702 Electromagnetic spectrum. Direct answers first, then deeper explanation — then practise with marking.
What makes electromagnetic waves different from sound waves?
Electromagnetic waves are transverse, can travel through a vacuum, and always move at the speed of light in a vacuum. Sound waves are longitudinal, require a medium to travel, and are much slower.
Why is visible light such a small part of the electromagnetic spectrum?
Our eyes have evolved to detect only a narrow range of wavelengths (400-700 nm) within the vast EM spectrum. This range is likely due to the specific light energies most abundant and useful on Earth's surface for vision.
How is the energy of an electromagnetic wave related to its position in the spectrum?
The energy of an EM wave is directly proportional to its frequency and inversely proportional to its wavelength, as described by the Planck-Einstein relation . So, gamma rays (highest frequency, shortest wavelength) carry the most energy, while radio waves (lowest frequency, longest wavelength) carry the least.