Physics
Why does'nt the hydrogen atom emit X-rays?

It is very small in size
Its energy levels are very close to each other
It has only one electron
It is highly electropositive

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Physics
Lightning is produced when

Similar charges of electricity rush towards each other and then get repelled
Water vapour produces electricity in the clouds
Clouds strike against impurities in air and the friction burns up these impurities
Strong opposite charges in different clouds break down the resistance offered by the intervening air

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Physics
Rainbow is due to

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

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