The visible light is released and absorbed by a small packet called photons and shows both wave and particles characteristics and this property are known as wave-particle duality.
Light waves can be measured in two different ways
- Â Â The amplitude of the wave
- Â Â Â Frequency of the wave along with the number of waves per second.
These waves are categorised according to the frequencies that have similar characteristics in the electromagnetic spectrum of the light. The subcategories of each spectrum vary according to the wave frequency.
The colour of these lights depends on the reflection quality from the objects on which the white light falls on. For example, the white wall appears because the wall reflects back all the colours. Â
Any particular colour that looks from any surface is the colour that is reflected from the object when the light falls on it.
The Light Wave and Colour Formula:
 c = ν  x λ
where,
c = speed of light
v = frequency
λ= wavelength
Solved Examples
Example 1:Â Calculate the frequency of the violet colour whose wavelength is 400 nm.
Solution
Given:
Wavelength = 400 nm
We know that c (Speed of Light ) = ν (Frequency ) × λ ( Wavelength)
ν = c / λ
 ν= (3×108)  / (4.00×107)
Therefore, frequency = 7.5 Hz
Example 2: Determine the wavelength and predict the colour of light which has a frequency of 6.00 × 1014 Hz, given the speed of light is 3 × 108 m / s.
Solution:
Given:
Frequency = 6.00 x 1014 Hz
We know that, C (speed of light ) = ν (frequency ) × λ ( wavelength)
λ = c / ν
λ = (3×108) / (6.00 × 1014)
Therefore, λ (wavelength) = 0.5 × 10 -6
                = 5000 × 10-9 m
                = 5000 nm
The colour of the wavelength of 5000 nm is green.
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