These wavelengths range from nm at the red end of the spectrum to nm at the violet end. White light is actually made of all of the colours of the rainbow because it contains all wavelengths, and it is described as polychromatic light.
Light from a torch or the Sun is a good example of this. Light from a laser is monochromatic, which means it only produces one colour. Lasers are extremely dangerous and can cause permanent eye damage.
Objects appear different colours because they absorb some colours wavelengths and reflected or transmit other colours. The colours we see are the wavelengths that are reflected or transmitted.
Red light is the only light that is reflected from the shirt. If only blue light is shone onto a red shirt, the shirt would appear black, because the blue would be absorbed and there would be no red light to be reflected.
White objects appear white because they reflect all colours. Black objects absorb all colours so no light is reflected. The retina of our eyes contains two types of photoreceptors — rods and cones. The cones detect colour. The rods only let us see things in black, white and grey. Our cones only work when the light is bright enough, but not when light is very dim.
This is why things look grey and we cannot see colours at night when the light is dim. There are three types of cones in the human eye that are sensitive to short S , medium M and long L wavelengths of light in the visible spectrum. These cones have traditionally been known as blue-sensitive, green-sensitive and red-sensitive, but as each cone is actually responsive to a range of wavelengths, the S, M and L labels are more accepted now.
These three types of colour receptor allow the brain to perceive signals from the retina as different colours. Some estimate that humans are able to distinguish about 10 million colours. The primary colours of light are red, green and blue. 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. 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. 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. The way coloured light mixes is very different from the way that paint does. When light hits a surface, some of it is absorbed and some of it is reflected.
The light that is reflected is the colour of the object in that light. For example, a blue object absorbs all the colours of the spectrum except blue: it reflects blue light. The table gives some more examples, displaying the colour of light shining on an object, the colour s absorbed by an object, the colour reflected by an object in this light and the colour of an object seen in this light.
Objects appear black in white light because they absorb all colours and reflect none. Objects also appear black in any single colour of light if their colour is not the same as the light. For example, a green object appears black in any other light than green or white which contains green because there is no green light shining on it to reflect into your eyes. Colour White light is a mixture of many different colours, each with a different frequency.
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