What are X-Rays? Everything You Need to Know

x-rays vs gamma rays

What are X-Rays? Everything You Need to Know

If you’ve ever broken a bone or traveled to the airport, there’s a good chance you’ve been exposed to X-rays. This form of radiation can be dangerous at high levels but when used properly has many useful applications. Continue reading for a deep dive into the aspects of X-rays and how they influence your life.

What Are X-Rays? Complete Explanation

X-rays make up one of seven parts of the electromagnetic spectrum, which covers the entire range of energy waves in our universe. This portion lies at the shorter end of the spectrum, with its frequencies found between ultraviolet radiation and gamma rays. X-rays are so small that their wavelength can measure as small as the diameter of an atom.

When studying the electromagnetic spectrum, researchers will use one of three metrics: frequency (hertz or Hz), wavelength (meters or m), or energy (electron volts or eV). The measurement that researchers use typically depends on which one is easier to write out.

Due to the incredibly minuscule size of X-rays, scientists often define them based on their energy level. While there is no hard definition for the energy of this type of radiation, they’re usually found between 100eV and 200keV.

x-rays vs gamma rays
An X-ray is a penetrating form of high-energy electromagnetic radiation.

An accidental discovery in the late 1800s, X-rays occur naturally through the acceleration of electrons in atoms. This is most noticeably seen in the pulling apart of celestial bodies such as stars and gas clouds. While the resulting energy is usually very sporadic, researchers have discovered methods of accelerating electrons in a more concentrated setting. 

Similar to gamma rays, X-rays have energy levels powerful enough to alter the composition of atoms. Because of this characteristic, exposure to high levels of X-rays can result in sickness, physical harm, and even death. To prevent the hazardous effects of this type of radiation, researchers and professional personnel use dense materials such as lead as shielding.

While they possess dangerous potential, X-rays are particularly useful in peering through objects. When used safely, this radiation can assist in imaging the brain and body. X-ray radiography is also used to examine the contents of shipping containers and personal luggage at the airport.

X-Rays: An Exact Definition

According to the National Center for Biotechnology Information, “X-rays belong to the group of electromagnetic rays, hence, they follow the rules of electromagnetic radiation. Electromagnetic radiation transports energy, also called radiant energy, through space by waves and photons, just as radio waves, the visible light or microwaves.”

The government agency goes on to define the wavelength of X-rays, which “lies in the range of 0.01 nm up to 10 nm. This corresponds to an energy range of 100 keV down to 100 eV.”

The Australian Radiation Protection and Nuclear Safety Agency (ARPaNSA) supports this information, stating that X-rays “originate from the electron cloud of an atom. This is generally caused by energy changes in the electron, which moves from a higher energy level to a lower one, causing the excess energy to be released.”

Where Do X-Rays Come From?

As the ARPaNSA explains it, X-rays come from the acceleration of electrons within an atom. As they increase in energy, the electrons either crash into other materials, get lodged out of place, or fly out of their orbit completely. This causes the atom to become unstable, requiring it to equilibrate, which creates X-ray energy.

In natural settings, we typically see this happen aggressively in binary celestial systems. These systems consist of two bodies, one more massive than the other. The massive celestial body, usually a form of a black hole or neutron star, uses its gravitational pull to rip apart its partner entity. The immense power involved in tearing apart a star causes electrons to rapidly energize, emitting high-frequency radiation.

While these celestial bodies create an incredible amount of X-ray energy, they rarely penetrate the earth’s atmosphere. This is because their photons are so small that when they crash into oxygen or nitrogen atoms, they trade places with an electron. As a result of this process, called photo-electric absorption, researchers have to rely on weather balloons and orbital satellites to study the radiation.

How Do You Create X-Rays?

Unlike gamma rays, which involve the settling of a nucleus to produce its radiation, X-rays rely on the settling of an entire atom. Because of the added complexity in this settling, X-rays are more challenging to direct than their high-frequency partner. However, this doesn’t make it impossible to use properly controlled.

To create X-rays in an applied setting, researchers accelerate electrons in a tube using a voltage drop and direct them at a target. When the electrons or target atoms slow down, they release high-frequency radiation in a cone. Computed tomography (CT) scanners use these tubes to map objects in 3D.

Scientists also create X-rays using synchrotrons, which accelerate electrons in a massive, hollow ring. This ring, which is about the size of a football field, has magnets that circulate it to direct the electrons as they speed up. Synchrotrons provide the space needed to concentrate X-ray energy into a powerful beam but are only used for research purposes. 

Who Discovered X-Rays?

As far back as 1869, researchers observed unidentified radiation coming from discharge tubes while experimenting with electron beams. However, it wasn’t until 1895 that German physicist Wilhelm Röntgen accidentally discovered their existence while experimenting with the beams using a variety of discharge apparatus.

Working with fluorescent effects caused by the electron beams, Röntgen found that materials in his laboratory were shimmering despite the lack of light. The shimmering was speculated to be a new type of energy ray, similar to that of ultraviolet and infrared.

Röntgen temporarily named the radiation “X-ray”, with the “X” referring to the mathematical designation for something unknown. After its confirmation following several radiograph images, the radiation was renamed “Röntgen ray.”

What Are the Applications of X-Rays?


X-ray imaging creates pictures of the inside of your body.

While X-rays feature high energy levels, they don’t penetrate as many materials as gamma rays. With the right protection, this allows medical professionals to map the human body without causing damage. Common applications for X-ray imaging include mammograms, dental, and body CT.

In specific cases, oncologists can use this type of radiation to kill cancer cells. Professionals direct X-rays at the target cells to strip their atoms of electrons, which can weaken or destroy them. However, because this type of radiation is difficult to focus on, it can also cause damage to normal cells.


In the metal industry, researchers use X-ray crystallography to determine the quality of dense materials. This process involves measuring the diffracted beams of high-frequency waves by their angles and intensities to create an image of the density within the material.

In other industries, businesses use X-ray imaging to explore the components within an object. This is commonly seen in transportation, where shipping containers are exposed to X-rays to create an image of the objects inside. Airport security also uses this to check suspicious people for things on their bodies.


Because the atmosphere absorbs this energy frequency, astronomers rely on weather balloons and orbital telescopes to observe X-rays in space. In particular, studying this frequency helps us understand the relationship between celestial objects and black holes. 

One of the more exciting observations that come with X-ray astronomy is the dynamics of supermassive black holes. These objects are millions of times denser than the Sun and absorb the celestial bodies that fall within their gravitational pull.

Examples of X-Rays in the Real World

Single-Frame X-Ray Tomosynthesis

One of the newest developments in X-ray technology, single-frame X-ray tomosynthesis (SFXT) uses a similar design as computed tomography. The equipment sacrifices the field of view and projection for a much higher resolution.

SFXT captures images at 30FPS, stitching together aspects that reveal up to 100 times the detail. This technology allows researchers to study the mechanics of body parts as they function.

Backscatter Technology

Where traditional X-ray machines would transmit radiation through the human body, airports are adopting backscatter machines to reduce exposure to harmful waves. Backscatter X-ray imaging detects radiation that reflects from people, requiring less powerful rays. These machines are being used to discover hidden objects such as weapons, liquids, and other contraband.

Chandra X-Ray Observatory

Part of the four Great Observatories, the Chandra X-ray observatory is the largest space telescope of its kind. Launched in 1999, Chandra uses four cameras and spectrometers to study massive celestial objects as they interact with each other. Some of Chandra’s most significant discoveries include a new type of black hole, the shadow of a galaxy being consumed by a large one, and evidence for dark matter.

X-Rays: Further Reading

Despite their powerful energy, X-rays help us understand the workings of our universe and our inner selves. This form of electromagnetic radiation makes up a part of the light waves that influence our lives. For more on the applications of radiant energy, check out the articles below.

Frequently Asked Questions

How do x-rays compare to gamma rays?

While both x-rays and gamma rays are ionizing, high-frequency energy waves, x-rays are larger and less powerful. Because of their energy difference, they penetrate fewer materials, making them ideal for mapping the human body.

The two types of radiation also differ in their emission process; gamma rays rely on settling a nucleus in an atom, while x-rays rely on settling the electrons.

What are x-rays' simple definition?

X-rays are a type of radiation on the electromagnetic spectrum. Electromagnetic radiation transports energy through space along waves or photons. X-rays are characterized by their high frequencies and high energy levels.

What are x-rays made of?

X-rays are made of light energy that travels at an incredible frequency. They are the result of accelerating electrons so fast that they alter the composition of an atom.

Where are x-rays used?

X-rays have applications in several industries, including medicine, transportation, and space. Common uses include x-ray imaging, crystallography, and screening. NASA also uses x-ray spectroscopy to study celestial bodies.

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