Which Have the Longest Wavelength: Light Waves, X-rays, or Radio Waves

Wavelength makes up the fundamental difference between two EM waves. The element decides the wave’s visibility to human eyes and proportionally links to its frequency. To grasp the specifications of the seven waves in the electromagnetic spectrum, you must know about their wavelengths.

So, which have the longest wavelength: light waves, X-rays, or radio waves? The answer is radio waves. Since the ray has longest wavelength, it is less absorbed by particles on the way. That is why you can make a phone call in a closed room and still hear the other end perfectly.

What is Wavelength?

Surrounding you are applications of EM waves: the microwave oven that heats your food, the TV remote control that changes your channels, the cellular networks that connect you to millions of others, and even the white light that comes from the Sun.

All EM waves have distinctive shapes, lengths, and characteristics, which is why they serve different purposes in your daily life. Learning the wavelength is one way to differentiate one EM radiation from another.

So, what is wavelength? It is the distance between two adjacent points on the same wave. You can measure from any point of one wave (the peak or bottom, for example) to its neighboring identical point.

The wavelengths of EM waves vary from time to time, changing when the waves travel through different mediums or stand still. In physics, the Greek letter lambda (λ) is used as a short form for wavelength.

Which Has the Longest Wavelength?

Among visible light, X-rays, and radio waves, what type of waves have the longest wavelength? It’s radio waves, which are not only longer than the other two but also the longest wavelength in the electromagnetic spectrum.

The wavelength of radio waves ranges from one millimeter to hundreds of kilometers. Some of them are even as large as our planet. Radio waves have endless applications in our day-to-day life, from television and FM radio broadcast to mobile phones and wireless networks.

When you tune into an FM channel, you are choosing a specific wavelength that transmits the signals of the station. The wavelength of a 90-MHz channel, for example, is usually around 3.3 meters.

As radio radiations has the longest wavelength, they are less affected by particles on the Earth’s surface. They travel almost freely and thus can effectively carry data over long distances.

The wavelength of an EM wave can also tell us its frequency. Waves with the largest wavelength have the smallest frequency. Therefore the lowest frequency/energy in the electromagnetic spectrum belongs to radio waves, which are from 3 kilohertz to 300 gigahertz.

Which Has the Shortest Wavelength?

The wavelength range of X-rays is 0.01 to 10 nanometers, which is shorter than visible light and radio waves.

You shall see a huge difference when comparing X-rays’ longest wavelength to shortest wavelength of radio waves. Radio waves’ shortest length is only 1 mm, but it is already 100,000 times larger than the longest X-rays (one million nanometers equal one millimeter).

With short wavelengths, X-rays are more easily absorbed by certain particles. Your bones and teeth, for example, absorb X-rays, while soft tissues like your skin don’t. So, when doctors send X-ray radiation through your body, they can see the image of your bones and teeth on the screen.

Frequently Asked Questions

What is the wavelength of visible light?

Visible light is the small portion of the EM spectrum that human eyes can detect. As light waves travel through different mediums, they generate the seven colors of the rainbow. Each color carries a unique range of wavelengths.

Wavelengths of Colors in the Visible Spectrum
Color Lowest Length Highest Length
Violet 380 nm 450 nm
Blue 450 nm 495 nm
Green 495 nm 570 nm
Yellow 570 nm 590 nm
Orange 590 nm 620 nm
Red 620 nm 750 nm

Visible light, in general, has wavelength ranges from 380 to 700 nanometers.

Are radio waves the same as visible light?

Both are EM waves but are different in many aspects: wavelength, frequency, and energy. Your eyes can detect visible light (an example is the Sun) but not radio waves.

So, while visible light brings you the colors of the world, radio waves help carry data from one point to another.

What is the electromagnetic spectrum?

The electromagnetic spectrum contains seven types of waves. As these waves travel through space and the Earth’s surface, they adopt various shapes and lengths.

Radio waves are the electromagnetic waves with the longest wavelengths. They are used to transmit data in many networks, such as cellular mobile networks, mobile phones, and radios.

What are the other waves of the EM?

Besides radio waves, the EM spectrum contains:

  • Microwaves: Also known as heat waves, microwaves have the highest frequency among the seven EM waves.
  • Infrared: You can find infrared waves in the heat of the sunlight. They are also used in remote controls.
  • Visible light: They are the only EM waves visible to the naked eye. An example of visible light waves is the light bulb in your house.
  • Ultraviolet (UV) light: With wavelengths ranging from 10 to 400 nanometers, UV light is visible to some insects but not to human eyes. Though we typically associate them with sunburns, UV rays have useful applications like water treatment and phototherapy.
  • X-rays: The wavelength of X-rays stays in the lower range—from 0.01 to 10 nanometers. Their applications are mostly in the medical field.
  • Gamma Rays: These have the shortest wavelengths and the highest energy in the EM spectrum. Gamma Rays are used in radiotherapy to treat cancer.


To sum up, the answer to “Which have the longest wavelength: light waves, X-rays, or radio waves?” is radio waves—the radiation that carries information from place to place.

These waves help us learn a lot about the universe. Through radio telescopes, astronomers study the shapes and motions of planets, comets, and other astronomical phenomena.

Are you curious to learn more about radio waves? Browse our articles in this category for more interesting facts!

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