50 Interesting Facts About The Electromagnetic Spectrum

The sky is blue due to the scattering of sunlight off molecules of the atmosphere. This is more effective at short wavelengths. Therefore the light scattered down to the earth at a large angle with respect to the direction of the sun's light is predominantly in the blue end of the visible spectrum.

27. X-rays are faintly visible to the dark-adapted eye when it is close to an x-ray source. It is not known why this occurs and it is seen by humans as a blue-grey glow.

28. The range of wavelengths that a human eye detects and that is used for photosynthesis are roughly the same (400nm to 700nm). Most of the other wavelengths are largely absorbed by ozone, carbon dioxide, and water.

29. Both pure spectral yellow light (Wavelength ~580nm) and the additive of red and green lights can stimulate us to perceive the same yellow color.

30. Peeling scotch tape in a vacuum produces radiation powerful enough to X-ray the human body.

When illuminated by ultraviolet rays from a black light, scorpions glow in unnatural neon blue color. UV light that hits them gets converted by proteins in their exoskeletons into the light of a blue hue, which is visible to the human eye.

32. When green lasers such as the ones used in Christmas displays get very cold, they stop emitting green and instead emit an invisible infrared beam that can cause eye damage.

33. NASA has a Boeing 747 plane called SOFIA (Stratospheric Observatory for Infrared Astronomy) that houses an infrared telescope, which they use to peer at the black hole at the center of our universe.

34. When you use laundry detergent labeled as a "brightener," it doesn't make the clothing any cleaner or restore its color. It is a chemical that absorbs more light in the electromagnetic spectrum and re-emits fluorescent light to make the clothing appear brighter.

35. Wifi and Microwave ovens use the same frequency on the electromagnetic spectrum. This is why running a microwave near a wireless router can slow down your wifi connection, or make you disconnect entirely.

Meteors reflect radio waves and you can listen to them arriving in Earth's atmosphere on the radio.

37. Radios can pick up AM signals from stations broadcasting from beyond the horizon because the signals are reflected in the Heaviside Layer, a layer of ionized gas in the Earth's atmosphere, about 60-90 miles up. The Heaviside Layer acts as a mirror in the sky for radio waves.

38. Before we had man-made communications satellites, a technique called the "Moon bounce" was used to send long-range radio signals. Radio waves were sent up from Earth, bounced off the Moon, and then back down to a receiver on Earth. The technique is still used by some amateur radio operators.

39. MRI and CT Scans are both used to capture images within your body, but their biggest difference is that MRIs (magnetic resonance imaging) uses radio waves and CT (computed tomography) scans use X-rays.

40. Diamonds evaporate under UV light. When exposed to intense light pulses in the UV-C band (the harsh ultraviolet rays filtered out by the ozone layer), small pits on the diamond’s surface become visible in just a few seconds.

The reason why medicine bottles are orange or light brown is because of their ability to prevent ultraviolet light from degrading the contents through photochemical reactions, while still letting enough visible light through the bottle for the contents to be seen.

42. Short-wave ultraviolet light is an effective disinfection technique because it destroys microorganisms' nucleic acids and DNA, leaving them unable to perform vital cellular functions. It is 99.99% effective against bacteria, viruses, molds, and other pathogens.

43. Dynamic Phototherapy is a form of cancer treatment which has the known side effect of giving humans a slight level of night vision. The retina of the patients undergoing this treatment gains the ability to process light at wavelengths higher than the visible light spectrum.

44. We can't see atoms under an ordinary microscope because atoms are smaller than the wavelength of visible light. The smallest thing we can see with visible light contains 10 billion atoms.

45. Gold is yellow, unlike its grey neighbors on the periodic table, due to Einstein's special relativity. The electrons in gold are moving so fast (some over half the speed of light) that they have a relativistic contraction, shifting the wavelength of light absorbed to blue and thus reflecting a golden glow.

The upper bound of Extremely Low Frequency Radiation (mostly long radio waves) wavelengths is about 100,000 km, or 62, 000 miles. For comparison, the diameter of Saturn is around 75,000 miles.

47. Scientists have developed a Laser of a very specific wavelength that is able to refrigerate by causing the object hit to release a photon which carries away more energy in the form of light than it absorbs.

48. The color of the average mirror isn't white light or whatever it's reflecting. It's green. Most modern, mass-produced mirrors are made of a soda-lime-silica glass with a silver backing. This combination of materials reflects more green light than other visible wavelengths.

49. Bleaching a stain only conceals its appearance by altering its chemical structure and its associated wavelength of absorption/reflection. It would still be visible under a UV light.

50. To communicate with their submarines deep underwater and anywhere in the world, both the US and the Russians use ELF (Extremely Low Frequency) transmitters. These ELF transmitters have a wavelength of over 3600 kilometers and use the Earth itself as the antenna.