Question

(i) What is visible spectrum?
(ii) Why is red used as the stopping light at traffic signals?
(iii) Two triangular glass prisms are kept together connected through their rectangular side. A light
beam is passed through one side of the combination. Will there be any dispersion? Justify your
answer.​

Answer 1

Answer:

(i) Visible spectrum is a band of colors which are visible to human eye.     Example- Rainbow

(ii) The primary reason why the color red is used for stopping at traffic signals is that red light is scattered the least by air molecules. The effect of scattering is inversely related to the fourth power of the wavelength of a color. ... So red light is able to travel the longest distance through fog, rain, and the alike.

(iii) No there wont be any dispersion.Light get refracted when it changes medium. When the light changes medium there is a change in its speed, white light is mixture of lights of various wavelength,  each wavelength is refracted at different angle. In case of refraction by a prism, it  gets split into a band of light. But when two prisms are kept together and light is passed from one side,  it doesn't emerges as a band of light on the other side, because the second prism merges the band created by the first one and turns it into white light.

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Answer 2

Answer:

(i) visible spectrum is that in which we can see in the electromagnetic spectrum i.e light which ranges between 340-780 nm

(ii) red has longest wavelength due to which it can be seen from a long distance

(iii) white light will get dispersed into seven colours but in second prism it will get recombined to form white light

Explanation: