The Electromagnetic Spectrum (EMS)

Electromagnetic waves travel at the speed of light in a vacuum, but they slow down when passing through different media like water or glass.

Mechanical waves require a medium to propagate, whereas electromagnetic waves do not and can travel through the vacuum of space.

For a constant wave speed, frequency and wavelength are inversely proportional (v = f * lambda). As wavelength increases, frequency must decrease.

iPhones use radio waves in the microwave frequency range for cellular communication. While these are technically radio waves, they occupy the microwave portion of the electromagnetic spectrum (around 1-6 GHz). Option C is more specific and technically accurate for cellular bands.

Radio waves are commonly used for long-distance communication, including satellite transmissions, due to their ability to travel through the atmosphere.

The visible spectrum for humans typically ranges from approximately 380 nm (violet) to 700 nm (red).

Red light is at the long-wavelength end of the visible spectrum, typically around 700 nm.

Within the visible spectrum, violet light has the shortest wavelength and the highest frequency.

VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange, Red) lists colors from shortest wavelength (Violet) to longest wavelength (Red).

X-rays have higher energy and shorter wavelengths than both UV-rays and Infrared rays.

Ultraviolet rays have a much higher frequency than microwaves, which are on the low-frequency end of the spectrum.