What is the first law of thermodynamics? What are its implications?
Solution 6E: White light consists of light of seven different colours, with different frequencies. When these coloured lights pass through the prism, each of them deviates by different angles and we see the ‘VIBGYOR’ colours as shown below: Same is the case with rainbow. There are a collection of suspended droplets in the atmosphere that are capable of concentrating the dispersed light at angles of deviation of 40-42 degrees relative to the original path of light from the sun. As a result of which the seven colours of rainbow appears. Step1: a) As we move outward from the innermost band of the rainbow, the colour of the light changes from violet to red. Since, red light has highest wavelength and violet light has the lowest, thus, the wavelength increases on moving outward from the innermost band of the rainbow. Step2: b) Frequency of light is inversely proportional to the wavelength. It means, as the wavelength increases, frequency decreases and vice-versa. Thus, on moving outward from the innermost band of the rainbow, frequency decreases. Step3: c) As hydrogen emits light of certain definite frequencies only, therefore, if hydrogen discharge tube is used instead of sunlight as a light source, then, it will split into its various colours but what you would see is a small part of the hydrogen discharge rainbow. Most of the spectrum is invisible to the eye because it is either in the infra-red or the ultraviolet region.