When light strikes a surface, some of its energy is reflected and some is absorbed. The color a person perceives indicates the wavelength of light being reflected. White light contains all the wavelengths of the visible spectrum, so when the color white is being reflected, that means all wavelengths are being reflected and none of them absorbed, making white the most reflective color.
TL;DR (Too Long; Didn't Read)
As a form of energy called electromagnetic radiation, light travels in waves with some of its colors having longer wavelengths than others. The visible light humans see as the color white consists of a rainbow of colors in the electromagnetic spectrum that range from blue to red, with yellow, orange, green and multiple variations sandwiched between them, as in a rainbow after a storm. Blue and violet have shorter wavelengths and higher energy, and, at the opposite end of the spectrum, red wavelengths are longer, but have lower energy.
From Total to Zero Reflectivity
If the color of a surface is anything other than white, it means that it absorbs light of some wavelengths. For example, a surface that appears red absorbs yellow, green, blue and violet light, while reflecting red light. A surface that appears green absorbs all colors except green. White light is a combination of all colors -- as is apparent when you shine a white light through a prism -- so anything that appears white reflects all wavelengths of light. Black is the least reflective color, it's the color of a surface that absorbs all light.
Tints and Shades
If a surface isn't white, then the closer its color is to white, the more light it reflects. Pastel and off-white colors reflect more light than deep tones. Adding white to a color is called tinting the color, and it increases the color's reflectivity. The contrasting procedure is to add black to decrease the reflectivity. This is called shading.
Different Colors in Different Lights
An object that is white, would look red in a red-colored light because white contains all colors. But if a blue light were shined on a red ball, the color on the ball would be very dark, because the red color only contains red, not blue, so it absorbs the blue light instead of reflecting it. The color of an object depends on the light cast upon it. The only way to know the color of an object is to put it into sunlight or white light.
Darker colored objects heat up faster in the sun than light colored ones, which is why running across asphalt in bare feet can feel much hotter than walking across light-colored concrete. The reason is that darker colors absorb more of the different wavelengths of light energy, while white or light-colored objects reflect the light of most wavelengths.
Raspberry Pi is a series of what are essentially tiny computers that can fit in the palm of your hand. However, these nifty little tools offer a nearly endless amount of programming and computing applications, such as controlling robotic arms or automating when your coffee maker pours you a cup of Joe in the morning. The best part is that it doesn’t take years of study and thousands of dollars to learn how to use Raspberry Pi. The Raspberry Pi Mastery Bundle is on sale for $34 and can teach you how to use Raspberry Pi in less than a day.
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The Raspberry Pi is a modular computer you can use to learn computer programming and to create technology projects. It fits in the palm of your hand and costs about $35. Advanced Raspberry Pi enthusiasts build homemade, low-cost versions of commercially available products such as wearable technology and retro gaming consoles. Many go so far as to build highly creative inventions such as robots or a “Magic Mirror” that turns your mirror into an interactive smart device while you brush your teeth. Anyone who is eager to start with the Raspberry Pi can begin by honing their skills with the following projects.
The Raspberry Pi Setup
Before you begin a project, you need to set up the Raspberry Pi. Check out the Raspberry Pi Foundation’s setup guide for help with the necessary hardware and software. You need to download an operating system for the device. The official Linux operating system for Raspberry Pi is called Raspbian, and you can download it free from the setup guide. You can also buy it on a preloaded SD card that includes other operating systems you might need for some projects. Raspberry Pi models 3 and later have built-in Wi-Fi, while earlier models require a Wi-Fi dongle for any projects that rely on wireless internet access. Once the Raspberry Pi is set up, you can operate it using a keyboard, mouse, and a computer or television monitor. Detailed instructions for each of the following projects are available in the References section.
Photo Booth Project
In this project, you create a photo booth in your home to entertain guests. Instead of an actual booth that you sit in, the Raspberry Pi becomes a touch-screen operated camera that you mount to a wall or onto a tripod. Guests control the camera using the touch screen and then pose for a picture. The photos can be uploaded to Google Photos and also emailed to guests. Be as creative as you like when designing the enclosure for the device. For example, you could make your photo device look like an old-fashioned camera, an oversized instant film camera or an abstract art piece. In addition to the basic setup hardware you need for most Raspberry Pi projects, you also need a Raspberry Pi touch screen and a Raspberry Pi Camera Module for this project.
Robot Antenna Project
This project is an easy way to learn skills that will eventually prepare you to build highly functional robots. In this case, you make a drawing of a robot and wrap it around a cardboard tube. You construct the robot’s antenna out of an LED, two jumper wires and a resistor. You then attach the antenna to the robot’s head and connect it to the Raspberry Pi. Then, use a program in the Raspbian operating system that allows you to arrange existing pieces of code, or “coding blocks,” into a simple program. When complete, your robot beeps and its antenna flashes whenever you press the spacebar on your keyboard. Once you master that project, you can play with how many times the LED flashes or make other modifications.
Private Music-Streaming Service Project
Instead of paying for a subscription to one of the various streaming music services, you can turn your Raspberry Pi into a music server that allows you to stream your MP3 collection from any remote device, regardless of where you are. For this project to work, you need to have all the music you want to stream saved on an external hard drive. You assign the Raspberry Pi a static IP address so you can type the same URL into your computer or mobile device every time you want to stream your music. You then install a media streaming server on your Raspberry Pi and a compatible app to the mobile device or computer you’ll be using to listen. Most of these services are free or charge an almost-free fee.