We’re going blind if there’s no light, but what is light? What causes it and how does it happen? The light we see in our daily lives is a part of the electromagnetic spectrum known as visible light.
However, as shown in the image above, light can take many forms. This article focused on visible light and a bit of ultraviolet; the other forms of light will be discussed later.
Light occurs as a result of the photon, which is the fundamental particle that carries electromagnetic force. As we know, electrons in the atom can move to a higher orbit and build molecule bonds; when these electrons return to their original orbit, the energy released is a packet of light known as photons.
1. Blue is the warmest color
The human eye can detect wavelengths from 380 to 700 nanometers. The color we see daily are divided into seven colors, from the longest wavelength to the shortest: red, orange, yellow, green, blue, indigo, and violet.
Shorter wavelengths radiate higher energy thus hotter temperatures. Blue flame’s temperature is hotter than the orange-reddish one. Another example is the sun, it produces more yellow light because its surface temperature is 5.500°C, if the surface is cooler it would look reddish like the star Betelgeuse. If the Sun were hotter it would look blue, like the star Spica.
2. Gradient color of the sky
When the sunlight hit the earth's surface, it is scattered by molecules in the atmosphere. Air molecules scatter shorter wavelengths more effectively than the longer ones. Even though violet has the shortest wavelength, our eyes are more sensitive to detecting blue light, and the sun emits a higher concentration of blue light waves than violet. Hence, the sky appears blue.
The sky looks more colorful during sunset because the sun passes through a thick portion of the atmosphere, which caused the shorter wavelengths scattered away by the particle, leaving the longer wavelengths (yellow-reddish color) in the sky.
3. Color Theory
The color we see in an object is a reflection of the color that is not absorbed. For example, if we see a red flower, it means the flower absorbs all the light (in this case, color) except red.
A darker object absorbs more light, black absorbs all the light which causes more heat. As for the white color, it reflects all the light. That’s why it’s better to prevent dark clothes on hot sunny days.
4. It’s glow in the dark
I was a fan glow in dark toys when I was a child, I used to write with a magic marker on the wall and turn off the light immediately to see it glow. Growing up I learn this magic called photoluminescence.
Photoluminescence happens when high-energy light (usually ultraviolet) strikes the atom, causing the electron to move out to a higher orbit, the electron usually come back to its original orbit in one step and emits the same wavelength, but UV requires several steps, which causes the electron to emit a longer wavelength. Photoluminescence is divided into fluorescence, which glows shortly in the dark, and phosphorescence, which glows much longer.
Visible light only represents a small fraction of all types of light, but it is crucial for human life. The correction for this article is much appreciated since I’m still learning. In the next post, I’d like to learn about a sky phenomenon that is closely related to light. See you later, cheers!!
