Electromagnetic Spectrum

 

The electromagnetic spectrum is, in simple terms, the light spectrum.

It includes radio waves, microwaves, infrared, visible light, ultraviolet, X rays and Gamma rays. You need to know how damaging these waves are, as well as uses for each of them.

The waves of the electromagnetic spectrum are TRANSVERSE.

The speed of light in a vacuum is constant at 3x10^8m/s, so all of the elements of the electromagnetic spectrum have this wave speed.

The wave bands on the electromagnetic spectrum are in order of wavelength and frequency. Remember, since the speed of light is a constant, as wavelength increases, frequency decreases.

IMG_68A8880EA522-1.jpeg
IMG_3A12FB2A3C87-1.jpeg

Radio Waves and Microwaves

Radio waves have the largest wavelength on the electromagnetic spectrum. They also have the smallest frequency. The wavelength varies between around 1m to 1,000m. Radio waves are transmitted to allow us to communicate on our phones, listen to the radio or watch TV.

Microwaves are the second longest wavelength (around 1cm) and are also used in communications, as well as heating up food. Microwave ovens heat food up through microwave radiation heating up water molecules.

Electronic circuits are a source of radio waves and microwaves. Aerials can be used to detect radio waves and microwaves.

IMG_56DD2821098A-1.jpeg

Infra Red, Visible and Ultraviolet Light

Infra red light has a larger wavelength than visible light and has uses including TV remote controls, smoke detectors, and security detectors. Infrared light is emitted from warm objects and fire. It can be detected using electronic sensors and black-bulb thermometers.

Visible light is the light that we can see with our eyes. In visible light spectrum order from longest to shortest wavelength, and from lowest to highest frequency, is: red, orange, yellow, green, blue, indigo, then violet.

Ultraviolet (UV) light has a higher frequency than visible light and has a number of uses, as well as dangers. UV light allows us to synthesise vitamin D in our bodies, however UV light can also cause damage to our skin, potentially leading to DNA damage and subsequently some cancers. UV detectors can detect UV light.

IMG_C89004397567-1.jpeg

X-rays and Gamma rays

X rays are used in imaging of the body. These are extremely useful in the medical field, however can cause radiation damage to DNA.

Gamma rays, which are also discussed in the Radiation section of Nat 5 physics, have the highest frequency and shortest wavelength. It can be used for radiotherapy for certain cancers.

Fast electrons colliding with a metal target is a source of X-rays. These can be detected using a photographic film.

A source of Gamma rays is radioactive nuclei, and these can be detected using a photographic film or a Geiger-Muller tube.

Key Points!

  • Electromagnetic Spectrum

    This is the light spectrum and includes Radio waves, microwaves, infra red, visible light, Ultraviolet light, X rays and Gamma rays.

    You need to remember this spectrum in order of both frequency and wavelength.

    The speed of all of the waves in the electromagnetic spectrum is 3x10^8m/s

  • Different Electromagnetic Waves

    Know the sources, detectors and uses for Radiowaves, microwaves, Infrared, UV, X-Rays and Gamma Rays.

Any Questions?