Physics
The source of the Sun's energy is the process of

Thermionic emission
Nuclear fission
Nuclear fusion
Photoelectric emission

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Physics
Rainbow is due to

ionisation of water deposits
absorption of sunlight in minute water droplets
refraction and reflection of sunlight by water droplets
diffusion of sunlight through water droplets

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Physics
Why does the sea appear blue in colour?

Scattering of the sunlight by water molecules
Refraction of the sun light
Interference of the sun light from water surface
Reflection of the sun light from water surface

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