Physics
Lightning is produced when

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
Similar charges of electricity rush towards each other and then get repelled

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Physics
In the process of magnetisation of a bar

The entire bulk of the bar gets magnetised
Only the surface of the bar gets magnetised
Only the ends of the bar get magnetised
Only some parts of the outer layers of the bar get magnetised

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Physics
'Mirage' is an example of

Refraction of light only
Dispersion of light only
Total internal reflection of light only
Refraction and total internal reflection of light

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