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# The separation of white light into colours by a glass prism is a result of (A) Indifference (B) Diffraction(C) Total internal reflection(D) Variation of absorption with wavelength

Last updated date: 19th Sep 2024
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Hint: We know that the higher the absorbance of light by a solution, the lower the percent transmittance. The wavelength at which absorbance is highest is the wavelength to which the solution is most sensitive to concentration changes. This wavelength is called the maximum wavelength. It is also known that white light is nothing but colourless daylight. This contains all the wavelengths of the visible spectrum at equal intensity. In simple terms, electromagnetic radiation of all the frequencies in the visible range of the spectrum, appearing white to the eye, is called white light. Based on this concept we have to solve this question.

We know that as light passes through a prism, it is bent, or refracted, by the angles and plane faces of the prism and each wavelength of light is refracted by a slightly different amount. As a result, all of the colours in the white light of the sun separate into the individual bands of colour characteristic of a rainbow. Since violet light has a shorter wavelength, it is slowed more than the longer wavelengths of red light. Consequently, violet light is bent the most while red light is bent the least.
Thus, we can conclude that white light can be split up to form a spectrum using a prism. The shorter the wavelength of the light, the more it is refracted. As a result, red light is refracted the least and violet light is refracted the most causing the coloured light to spread out to form a spectrum. Prisms bend different colours to different amounts. So, when you shine a flashlight in, all of the different colours bend differently and get separated. (This is how you get a rainbow - by spreading the colours apart.). So, when you shine a laser through a prism, there's nothing to be separated, and the light stays together.
Therefore, the separation of white light into colours by a glass prism is a result of indifference.

Hence, the correct answer is Option A.

Note: We should know that diffraction refers to various phenomena that occur when a wave encounters an obstacle or a slit. It is defined as the bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. Diffraction is caused by one wave of light being shifted by a diffracting object. This shift will cause the wave to have interference with itself. Interference can be either constructive or destructive. When interference is constructive, the intensity of the wave will increase.
On the other hand, total internal reflection, in physics, is the complete reflection of a ray of light within a medium such as water or glass from the surrounding surfaces back into the medium. The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle. For total internal reflection occurs when the light is travelling from a denser medium into a less dense medium (which is glass to air) the angle of incidence must be greater than the critical angle.