The white light around us is made up of a mixture of different colors of light. The surfaces of objects absorb some colors and reflect others back. Our eyes see only the colors that are reflected. An object that reflects all the colors of light appears white. An object that absorbs all the colors, looks black. A tomato absorbs all the colors except red, which it reflects back to us. You get the picture!
Tell me more: electromagnetic spectrum
Light is part of a continuous band of energy called the electromagnetic spectrum, which is made up of waves of radiation with different wavelengths (distance between two peaks or troughs of the waves). Apart from light, all electromagnetic waves are invisible to the human eye.
Television: Uses radio waves.
Radio Waves: Used to carry radio signals around Earth. Such as used in controlling robots through remote controller.
Microwaves: Cooking is a common use for microwaves.
Radar transmitter: Sends microwaves through the air. Such as in radar tracking system.
Visible light: What humans can see – red, orange, yellow, green, blue, indigo, violet.
Infrared rays: We cannot see, but can feel the heat emitted by these rays. Such as an electric iron.
Ultraviolet rays: Invisible rays that can cause damage to our eyes and skin. Like Sun-rays.
X-rays: High-energy rays used in medicine to check people’s bones.
Gamma rays: Harmful, cancer-causing rays produced by radioactivity.
What about you
Even if you could travel at the speed of light (which scientists are pretty sure is impossible), light would always be traveling away from you at the same speed.
What’s in a name?
“Laser” is short for Light Amplification by Stimulated Emission of Radiation. A laser passes light or electricity through a gas or a crystal to produce a concentrated jet of light powerful enough to cut through metal and precise enough to perform surgery.
Primary colors of light
When beams of all three of the primary colors are mixed together in equal quantities they form white light.
By combining the primary colors in different proportions any color can be made. This is how the color is produced on a TV screen.
Secondary colors of light
when mixed together in equal quantities, the primary colors of light form the secondary colors.
red + green = yellow
blue + red = magenta
green + blue = cyan
Printing colors
We can see the different colors in any print because the in pigments absorb certain colors of light and reflect others. Printers mix yellow, magenta, and cyan ink to create colors. Mixing all three together creates a muddy brown, so printers must also use a black ink.
FAST FACTS: Rainbow
- A rainbow appears when light passes through raindrops.
- Inside each raindrop, the sunlight is bent and split into the colors of the spectrum:
red
orange
yellow
green
blue
indigo
violet - You can also see a rainbow when the sun is behind you and the rain is falling in front of you.
- From an airplane rainbow form a complete circle.
- There are “mnemonic” word tricks to help you remember the colors of a rainbow:
Colorful triangle
Just like a raindrop, a prism (triangle of glass) changes the direction of tight passing through it. This is called refraction. The prism bends the wavelenghts, splitting the white light into a spectrum of colors.
In numbers
8
The number of minutes it takes for the Sun’s light to travel the 149,000,000 km (93,000,000 miles) to reach Earth. We see the Sun the way it looked eight minutes ago.
2000
The number of light waves that would fit in a millimeter (0.04 in).
20
The number of times more men than women that are affected by red/green color blindness. The ability to detect color depends on cells in the retina at the back of the eye that detect particular parts of the spectrum. Some of these are missing or inactive in a color-blind person.
You won’t believe it!
Light travels through space at 300,000 km/sec (186 miles/sec). A beam of light can travel around the world seven times in one second.