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two are inversely proportional to each other. The wave-length of red is longest while that of violet is shortest. Waves slightly longer than visible red colour are called infrared while those shorter than violet colour are called ultraviolet. But all the colours of visible light together with infrared and ultraviolet represent only a small part of a band of radiations extending from high-energy X-rays to low energy radio waves. The higher the energy, the shorter the wave-length. The following table shows the wave-length and frequencies of the visible spectrum:
Colour
Wavelength
Frequency (Vibrations per second)
Red Orange Yellow Green Blue Indigo Violet
7400-6200 A 6200-5850 A 5850-5750 A 5750-5000 A 500(0-4450 Ao 4450-4350 A 4350-3900 A
400-500 x 1011 500-540 x 1017 540-550 x 101 550-600 x 1011 600-660 x 1011 660-675 x 1011 675-760 x 1011
TA=
cm.
1000000
Colour of an Object
The colour of an object depends on the kind of light it sends to the eye. This depends on both (i) the nature of the light falling on an object and (ii) the colours in that light which its surface reflects, absorbs or transmits. If the light falling on a surface lacks some colours, the light reflected from the surface will also lack these colours. If a surface looks
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