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What’s the opposite of blue light?

What’s the opposite of blue light?

Blue light has become a well-known term in recent years, as the effects of blue light exposure from our devices has come under scrutiny. Blue light is a high-energy wavelength of light that can affect the circadian rhythm if exposed to it before bedtime. With the increase in screen time from computers, phones, and TVs, there is a growing concern over blue light’s impact on sleep and eye health. This begs the question – what is the opposite of blue light? Let’s explore.

What is Blue Light?

To understand the opposite of blue light, we first need to understand what exactly blue light is. Blue light is a visible light that has a wavelength between 450-495 nanometers (nm). It is emitted naturally by the sun but also comes from man-made light sources like LEDs and fluorescent lighting. Here are some key facts about blue light:

  • Part of the visible light spectrum – Blue light has one of the shortest wavelengths and highest frequencies of visible light.
  • Emitted from digital screens – TVs, computers, smartphones, and tablets emit high amounts of blue light from their screens.
  • Associated with eye strain – Staring at blue light for extended periods can lead to digital eye strain and fatigue.
  • Disrupts circadian rhythms – Blue light exposure at night suppresses melatonin production which can impair sleep.

While blue light is not inherently bad, excessive exposure in the evening from electronics has been linked to problems with sleep, eye health, and attention. This has created a demand for solutions that block or filter out blue light from our devices and environments.

Characteristics of the Opposite of Blue Light

If blue light is a high energy short wavelength light, then the opposite would have the following characteristics:

  • Longer wavelength – The opposite would have a longer wavelength than blue light, further into the visible or infrared spectra.
  • Lower frequency – With a longer wavelength comes a lower frequency of light waves.
  • Less energy – Longer wavelength light is lower in energy than short wavelength blue light.
  • Does not disrupt circadian rhythms – It would not suppress melatonin production at night.
  • Does not contribute to eye strain – It would be easier on the eyes and visual system.

With these factors in mind, let’s look at what the potential options are for the opposite of blue light across the light spectrum.

Infrared Light

Infrared light has the longest wavelengths of light that humans can partially perceive. It ranges from 700 nm to 1 mm, just beyond the visible red light spectrum. Here are some key facts about infrared light as related to blue light:

  • Very long wavelengths and low frequencies compared to blue light.
  • Commonly felt as radiant heat from sun and fires, but not visible to human eyes.
  • Does not impact circadian rhythms or melatonin production.
  • Does not contribute to eye strain or digital eye fatigue.
  • Used in IR remote controls, night vision cameras, and fiber optic communications.

While infrared light has properties opposite to blue light, the drawback is that it is imperceptible to human vision. We cannot see or experience infrared light directly. So while it technically qualifies, it may not be the most meaningful opposite to blue light for practical use cases.

Red and Orange Light

Moving down the visible light spectrum, red and orange light have significantly longer wavelengths and lower frequency than blue light. Here is how red and orange light compare:

Color Wavelength Frequency
Blue 450-495 nm ~668-605 THz
Green 495-570 nm ~606-526 THz
Orange 590-620 nm ~508-484 THz
Red 620-750 nm ~484-400 THz

Red and orange light have much longer wavelengths and lower frequencies than blue or green light. This makes them safer for nighttime exposure. In fact, orange/red light is commonly used for night lights and reading lamps to not disrupt melatonin.

The downside is that red and orange are not viable for computer and phone displays. But they are promising candidates for the conceptual opposite of blue in terms of wavelength and frequency.

Amber and Yellow Light

Intermediate to red/orange and blue/green are amber and yellow light. Amber lightbulbs are already used to filter out blue light exposure from screens and devices at night. Here is how amber and yellow compare to blue light:

  • Longer wavelengths (~580-590 nm) than blue light
  • Lower frequency amplitudes
  • Very little blue light emitted
  • Better for circadian rhythms at night than blue light
  • Easy on visual system and eyes

Amber and yellow light seem to strike the best balance between the benefits of red/orange light while still allowing screens to be usable for humans. This makes amber/yellow light a strong candidate for the practical opposite of blue in consumer products.

Violet and Ultraviolet Light

At the other end of the spectrum from infrared is violet and ultraviolet light. This contains wavelengths shorter than blue light. Here is how it compares:

  • Very short wavelengths (380-450nm)
  • Higher frequency than blue light
  • More energy than blue light
  • Only ultraviolet rays with shortest wavelengths are invisible to humans
  • Mostly filtered by Earth’s atmosphere

While violet light is on the opposite side of the spectrum from infrared, it shares more similar traits with blue light in terms of frequency and energy. It does not counteract the effects of blue light on eyes and circadian rhythms. So violet light would not be considered the practical opposite of blue either.

Darkness and the Absence of Light

An interesting perspective is that the true opposite of blue light is not any kind of light – it is darkness! The absence of visible light means no wavelengths of light reaching the eyes. Here is how darkness compares:

  • No light wavelength exposure
  • No frequency or energy transmitted
  • Allows melatonin production for sleep
  • Eliminates risk of eye strain from lighting
  • Not practical for using screens/devices of course

While blocking all light is not feasible in the real world, darkness presents an intriguing concept of the complete absence of light as the counterpoint to blue light. But some lighting and screens are still needed for everyday life in practice.


To summarize, here are the key points on what could be considered the opposite of blue light:

  • Infrared light – As the longest wavelength light that is imperceptible yet still affects heat and motion.
  • Red/orange light – The longest visible wavelengths with minimal impact on circadian rhythms.
  • Amber/yellow light – Notable lower energy than blue light while visible to the human eye.
  • Darkness – The complete absence of visible light is the absolute counterpoint to blue light itself.

In practicality, amber/yellow light seems the best compromise as the opposite of blue when it comes to consumer accessible solutions to excessive blue light exposure. This makes filters and lighting that shifts blue light to amber/yellow wavelengths promising options for improving eye health and sleep hygiene.

Ultimately, the opposite or counterbalance to blue light is defined by lower frequency and energy across the light spectrum. Finding solutions that limit blue light exposure while allowing needed colors for screens and displays will be key to balancing the pros and cons of different wavelengths in our modern world.