Mostly the light that everyone experience on earth is from the sun.
People are too dependant on the light to live on. Light give out heat.
Without light our earth would feel cold, damp, and dark including huan.
People can fo a lot of thing with the help of sun like cooking or drying clothes,
which help in our daily life. Light is like god, which give living things life.
People invented torch from the inspiration of the sun. Let look at the detail of sun and other light source:
The Sun
The Sun is the star at the centre of the solar system.
The Earth and other matter including other planets, asteriods,
meteroids, comets and dust orbit around the Sun,
which by itself accounts for about 99.8% of the solar system's mass.
Energy in the form of light suppot most life on earth via photosynthesis
and drives Earth's climate and weather.
Although the Sun appears white but actually is a combination of seven colours.
The Star
A star is massive, luminous ball of plasma(ionized gas) stars from together
to form galaxies(massive, gravitationally bound system consisting of stars)
and they dominate the visible universal. The nearest star to Earth is the Sun,
which is the source of most of the energy of the Earth, including daylight.
Other stars are visible in the night sky, when they are not outshone by the Sun.
A star shines because nuclear fusion in its core releases energy which traverses
the stars; intend then radiates into outer spaces. Without stars,
life and most atomic element present in the Universe would not exist.
The incandescent light bulb
The incandescent light bulb is the source of artificial light that works by
incandescent, an electrical current passes through a thin filament,
heating it and causing it to be become excited, releasing thermally equilibrated
photons in the process. The enclosing glass bulb prevents the oxygen in the air
from reaching the hot filament, which otherwise would be destroy
rapidly by oxidation.A benefit of the incandescent bulbs is that they can
produce a wide range of voltages, from just a few volts up to several thousand volts.
Because of their poor luminous efficacy, incandescent light bulbs are gradually
being replaced in many applications by (compact) fluorenscent lights, high-intensity
discharge lamps.
Light that strikes an object can be reflected, absorbed or transmitted. Firstly a plane mirror produces an image that is upright and the same size as the object. A concave mirror can form either virtual images or real images. Images formed by convex mirrors are always virtual.
When light rays hit the surface of a medium at an angle, they bend or change directions. The type of image formed by a convex lens depends on the position of the object in relation to the focal point. Concave lenses produce only virtual images.
You see an object as the color of the light it reflects. The primary colors of light are red, green, blue. As pigments, found in paints and other things, are added together fewer colors of light are reflected and more are absorbed.
You see objects because of a series of steps that involve the structures of a series of steps that involve the structures of the eye and the brain. Lenses can correct some vision problems such as nearsightedness and farsightedness.
Light is everywhere in our world. We need it to see: it carries information from the world to our eyes and brains. Seeing colors and shapes is second nature to us, yet light is a perplexing phenomenon when we study it more closely.
Here are some things to think about:1.Our brains and eyes act together to make extraordinary things happen in perception. Movies are sequences of still pictures. Magazine pictures are arrays of dots.2.Light acts like particles-little light bullets-that stream from the source. This explains how shadows work.3.Light also acts like waves-ripples in space-instead of bullets. This explains how rainbows work. In fact, light is both. This "wave-particle duality" is one of the most confusing-and wonderful-principles of physics.
Color is such an everyday phenomenon that we don't usually give it a lot of thought. But colors can produce surprising effects, for example, in the way they mix together. We can also use color directly in science to learn about the universe.
here are some of the activities you can try out:
http://www.learner.org/teacherslab/science/light/color/index.html
Light conforms to certain rules. These rules are, for the most part, simple and sensible, but they create situations that can be counterintuitive or perplexing.
Here are some activities you can try out:
http://www.learner.org/teacherslab/science/light/lawslight/index.html
Seperation of white light into colours
Light from many sources,such as sunlight,appears white.When white light passes through a prism,however,it seperates into a spectrum of varied colours.The prism bends,or refracts,light of different colours at different angles.Red light bends the least and violet bends the most.Light entering a prism is refracted towards the normal,and the emerginf ray is refracted away from the normal,turning the ray through a considerable angle.Because the refractive index of a substance varies for the different wavelengths,a prism can spread out the various wavelengths of light contained in an incident beam and form a spectrum.
The color systems used by scientists and artists are totally different.An artist will mix blue and yellow paint to get a shade of green;a scientist will mix green and red light to create yellow.The printed page in a magazine is yet another system.
Now,lets seperate the two different kinds of color in the world.First,there's the color you can touch,such as the skin of the apple or a painted wall.These colors are part of the surface of an object.Next,there's the color you can't touch,such as a beam of light and the colors produced by your computer monitor.Colors generated by light are part of a color system.The tangible colors which are on the surface of objects or on the printed page are another color system.
Additive colour mixing
Additive colour mixing is the reproduction of any desired colour by adding together different amounts of just three colours,red,blue and green,which are called the additive primaries.
This is how the colours in TV pictures are produced.The back of a TV screen is covered with a regular array of dots of three kinds of materials called phosphors.One kind glows red when an electron beam inside the TV tube hits it.The other kinds glow blue,green,respectively.
Purple is created by stimulating the dots that glow blue and red.Yellow is created by red and green glowing dots.White is created by a mixture of red,green,and blue.
Subtractive colour mixing
Subtractive colour mixing is used in photographic transparencies and prints.Such pictures are made of transparent layers,each layer partly clear and partly coloured with one of the subtractive primaries-magenta(red-blue),cyan(blue-green),or yellow(a combination of red and green).White light shining on the picture is a mixture of red,green and blue light.In this print industry,cyan,magenta,yellow and black are used as the primary colors.When you mix all the colors,the result is grey.