Is all light the same?
Your eyes already know the answer. Explore what light really is, why photons race together through empty space, and why some “white” light feels so much kinder than others.
What is light, really?
Physicists use one phrase for light: electromagnetic radiation. Light is a travelling disturbance in an electromagnetic field. It behaves like a wave with electric and magnetic fields oscillating at right angles, and it comes in photons: massless packets of energy. Wavelength and frequency decide the colour and the energy of each photon.
- Light is electromagnetic radiation.
- An electromagnetic wave has electric and magnetic fields oscillating at right angles.
- Photons have no rest mass and carry energy in discrete packets.
- Frequency and wavelength set the colour and photon energy of visible light.
Slide from red to violet
Move the slider to change the wavelength of visible light. Watch how the colour and photon energy change, even though it is the same kind of radiation.
Shorter wavelength → higher frequency → higher photon energy.
Where visible light fits in the electromagnetic spectrum
Visible light is one thin strip of the electromagnetic spectrum. Radio waves and microwaves sit on the long-wavelength side. Ultraviolet, X-rays and gamma rays sit on the high-energy side. All of them are the same kind of thing: electromagnetic radiation with different wavelengths and frequencies.
- Radio wave: very long wavelength, very low frequency, very low photon energy.
- Infrared: just beyond red; we feel some of it as heat.
- Visible light: the band our eyes can detect, from red to violet.
- Ultraviolet: higher energy; useful in small doses, harmful in large ones.
- X-ray and gamma ray: extremely short wavelength and very high photon energy.
Do all photons move at the same speed?
In empty space, every photon moves at the speed of light in a vacuum. Change the medium and light slows down because it interacts with atoms in the material. The electromagnetic wave is absorbed and re-emitted; the result is a lower effective speed through air, water, glass or acrylic.
- All electromagnetic waves travel at the same speed in a vacuum.
- Different materials give different effective speeds.
- The speed in a vacuum is constant and does not depend on colour or frequency.
How long does light take to cross your room?
Choose a medium and see how long light takes to travel 3 metres.
Do all kinds of light have the same energy?
No. Photon energy rises with frequency and falls with wavelength. Blue and violet photons carry more energy than red photons. Ultraviolet, X-rays and gamma rays carry far more. Brightness also matters: total energy depends on how many photons arrive each second.
- Higher frequency → shorter wavelength → higher photon energy.
- A bright red lamp can deliver more total energy than a dim blue lamp if it emits many more photons.
- Glare, spectrum and flicker all influence how easy reading feels.
Energy vs number of photons
Change the colour and brightness to see how total energy shifts.
Why does some “white” light feel harsh?
Two lamps can both look white but have very different spectral power distributions. Many white LEDs are built on a strong blue spike with missing deep reds. Your eyes adapt, but the effort can cause eyestrain. A smoother, more complete spectrum—especially deep red—lets text stay crisp and calm.
- Standard LEDs often have a blue spike and thin reds.
- Natural daylight is balanced but not always available.
- A rebuilt spectrum with deep red support makes black text look truly black.
Compare three “white” lights
Switch between these lights and see how the spectrum and text clarity change.
Standard LED: Harsh blue spike, missing deep reds. Eyes work harder.
Natural daylight: Full, balanced spectrum; the natural benchmark.
Serious reading light: Balanced with deep red emphasis; text stays crisp.
Quick answers about light and speed
Tap to reveal. No fluff—just the essentials your eyes care about.
Changing the light changes what you see
You cannot feel the spectrum of a light by looking at the bulb. You feel it in your eyes after twenty minutes of reading. We build lights to bring a more natural, complete spectrum to the page with a beam that is bright, controlled and steady.
For some people, that is simply more pleasant. For others, it is the difference between ten minutes of effort and an evening of relaxed reading. The easiest way to tell is to try one in your own home and see how your eyes respond.
Explore HD Essential and HD Pro lights →