The optical phenomenon that is primarily responsible for the observati

The optical phenomenon that is primarily responsible for the observation of rainbow on a rainy day is

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diffraction

interference

dispersion

reflection

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Answer is Wrong!

This question was previously asked in

UPSC CDS-1 – 2017

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A rainbow is formed when sunlight interacts with water droplets suspended in the atmosphere. This phenomenon involves several processes: refraction, dispersion, and reflection.

– When white sunlight enters a water droplet, it is refracted (bent) because the speed of light changes as it passes from air to water.
– As sunlight is composed of different colors (wavelengths), and the refractive index of water is slightly different for each color, the white light is split into its constituent colors. This splitting of white light into its spectrum is called dispersion. Dispersion is crucial because it separates the colors we see in a rainbow.
– The dispersed light then reflects off the inner back surface of the water droplet.
– Finally, the light is refracted again as it exits the droplet into the air, further enhancing the separation of colors.

While refraction and reflection are necessary parts of the process, dispersion is the specific phenomenon responsible for separating the different wavelengths of light (colors) that make up the visible spectrum, thereby creating the band of colors characteristic of a rainbow. Diffraction and interference are wave phenomena but are not the primary cause of the color separation in a typical rainbow.

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