Optics Mag is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Read more.

Infrared vs. Ultraviolet: Uses & How They Compare

Last Updated on

Infrared photography with great background

Infrared and ultraviolet are part of the electromagnetic spectrum, along with visible light. Whereas visible light has a wavelength between 380–760 nanometers (nm), infrared radiation has a wavelength of 700 nm to 1 millimeter (mm), longer than that of visible light. Ultraviolet radiation has a wavelength shorter than visible light and is usually between 10–400 nm.

Neither infrared or ultraviolet are visible to the human eye. Both have their uses. Ultraviolet is an essential source of vitamin D, for example, while infrared can be used to determine the temperature of objects like clouds.

Read on for more information on these types of electromagnetic radiation and to learn of some of their similarities and uses.

magnifying glass 2 divider Overview of Infrared

Virtually every object emits infrared radiation, except for objects that have no temperature at all or measure at absolute zero temperature. Objects of different temperatures give off different amounts of infrared, and while it is invisible to the human eye, we can use sensors and equipment to detect infrared levels.


infrared light
Image Credit: Quality Stock Arts, Shutterstock

Infrared has a wavelength of 700 nm to 1 mm and starts at the end of the red edge of visible light, hence its name. The frequency, or the number of waves that occur in a second, of infrared is between 430 Terahertz (THz) and 300 Gigahertz (GHz). Infrared travels in straight lines and cannot bend around corners.


Every object that is above a temperature of absolute zero emits some infrared radiation, and the hotter the object, the more infrared it emits. Even objects like ice emit infrared. The sun is the single biggest source of infrared on our planet.


Infrared Camera
(Image Credit: Minea Petratos, via Wikimedia Commons CC BY-SA 3.0)

Infrared has a host of uses, but because it is invisible to the human eye, we need to use sensors and displays to identify it. The best known of these is infrared vision or infrared goggles. These detect the infrared radiation given off by objects and display the resulting image with hotter objects appearing in brighter colors than cooler objects. Infrared is also used as a heat source. Infrared cookers and heaters benefit from this type of radiation. 

  • Infrared is easy to produce and control
  • Effectively, everything emits infrared
  • Invisible to the human eye
  • Travels in straight lines

magnifying glass 1 divider Overview of Ultraviolet

Ultraviolet (UV) sits at the other end of the natural light spectrum and is primarily emitted by the Sun, although artificial sources include tanning beds and some lights. It is essential for human survival but can be dangerous if you are overexposed to this type of radiation. Although invisible to the human eye, certain animals, such as bees, can see UV light.


Machine used for ultraviolet spectroscopy
Image Credit: Rabbitmindphoto, Shutterstock

Ultraviolet has a wavelength between 10–400 nm. It comes before the violent end of the visible light spectrum, which is why it’s named ultraviolet. Like infrared, UV is only capable of traveling in a straight line but, unlike infrared, not every object emits UV.


Very hot objects, such as the Sun, emit ultraviolet, and this is our primary natural source of UV. However, almost all forms of synthetic light produce some degree of UV. In some cases, this is the purpose of the light. Tanning beds, for example, use a UV emitting light to bathe the skin in this form of radiation. Halogen, mercury, and fluorescent lights all emit UV radiation. 


Plants Ultraviolet Light
Image Credit: Svyatoslav Balan, Shutterstock

Ultraviolet is an essential source of vitamin D for humans and other animals. It can also be used in agriculture to help plants grow and photosynthesize. It’s used in cleaning, especially for killing bacteria, which is why some water filters include UV lights. UV lamps may also be used to help with joint and muscle complaints.

  • Essential for life on the planet
  • Effective at killing bacteria
  • Only travels in straight lines
  • Overexposure can lead to skin and eye damage

magnifying glass 1 divider Types of Electromagnetic Radiation

Infrared and ultraviolet are types of electromagnetic radiation, along with visible light. There are generally considered to be seven types of electromagnetic radiation:

  • Radio – Radio waves have the longest wavelength of electromagnetic radiation. Although often thought of as being a type of soundwave because we think of radios, these waves are light. They are used to transmit data, which can include audio data. Radio waves are also used in medicine and to transmit visual data such as in television broadcasts.
  • Microwave – Microwaves are similar to radio waves. They are used in communication, although most of us instinctively think of their use in cooking food. Microwaves can pierce clouds, which infrared is incapable of doing, which gives these waves some benefit for communicating wirelessly with satellites, for example.
  • Infrared – Infrared (IR) heat is emitted by most objects, and, with the appropriate sensors and monitors, this makes it useful for viewing objects even in low-light and no-light conditions. However, infrared is only beneficial in near-field communications, such as communicating between your TV remote and the TV itself, as the IR waves would be absorbed by moisture in the atmosphere.
  • Visible Light – Visible light is the type of radiation that makes objects and everything around us visible to us. Objects absorb some, but not all, of the visible light radiation.
  • Ultraviolet – Ultraviolet light is emitted by the sun and other very hot objects. It can cause damage to living objects. This is why UV causes skin cancer, and it is why UV is beneficial in its capability to kill bacteria.
  • X-ray – X-rays are capable of piercing the skin, although they come unstuck when they come up against the force of bone. This is what makes them beneficial for X-raying the body and also in applications such as baggage scanning at airports.
  • Gamma Rays – Gamma rays have a wavelength shorter than the size of an atom (under 10 picometers). They are created by radioactive decay and are also produced by stars that go supernova. Gamma rays are very dangerous for living organisms but are absorbed by the Earth’s atmosphere before they have the chance to wreak havoc.

Practical Applications

Although they are both part of the electromagnetic spectrum, infrared and ultraviolet are quite different. The different properties of their waves mean that they have different practical applications:


  • Remote controls – Remote controls send infrared pulses, which are detected by receivers in televisions and other equipment. The signals are then translated by the equipment and a relevant function is performed.
  • Thermal imaging – Another common use of infrared is in thermal imaging. All objects give off infrared radiation and heat-sensitive thermal imaging cameras can detect tiny differences in the levels of heat and infrared, displaying different colors and shades of colors according to the heat variance. Thermal imaging cameras are used by the military but are also used in any circumstance with low or no light.
  • Astronomy – When limited to visible light, the universe can appear to be primarily black and with very few points of interest. Infrared detects heat, rather than light, and infrared astronomical cameras can be used to detect otherwise invisible celestial objects.


  • Vitamin D Stimulation – Although over-exposure to the sun’s UV rays can be very harmful, some UV is considered essential. When the skin is exposed to UV, it helps create vitamin D, which the body needs to synthesize calcium.
  • Sterilization – The same reaction that leads UV, specifically UVB, to cause skin cancer is also known to kill bacteria. As such, UV is regularly used as a method of antibacterial cleaning. It can be found in water filters. Artificially produced UVC is used to sterilize medical equipment.
  • Astronomy – Very hot objects produce UV and the hotter the object, the more UV is produced. As such, ultraviolet light can be used to help detect hotter parts of the Sun and other hot planetary objects like stars and nebulae. Because Earth’s ozone absorbs a lot of the UV, such observations need to be made outside Earth’s atmosphere, hence the Hubble Telescope’s use of UV imaging.
Plants Ultraviolet Light
Image By: Helga_777, Shutterstock

magnifying glass 2 divider Conclusion

Infrared and Ultraviolet are both forms of electromagnetic radiation and form part of the electromagnetic spectrum along with visible light, X-ray, and microwaves, as well as others. While infrared has a longer wavelength than natural light, ultraviolet has a shorter wavelength. Neither are visible to the human eye, and both have practical functions including communication and astronomy.

Featured Image Credit: chidchanok, Pixabay

About the Author Robert Sparks

Robert’s obsession with all things optical started early in life, when his optician father would bring home prototypes for Robert to play with. Nowadays, Robert is dedicated to helping others find the right optics for their needs. His hobbies include astronomy, astrophysics, and model building. Originally from Newark, NJ, he resides in Santa Fe, New Mexico, where the nighttime skies are filled with glittering stars.