Physics
The mercury and sodium street lamps light up because of :

Electron absorption
Atomic absorption
Electron emission
Atomic emission

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Physics
A metal ball and a rubber ball, both having the same mass, strike a wall normally with the same velocity. The rubber ball rebounds and the metal ball does not rebound. It can be concluded that

The initial momentum of the rubber ball is greater than that of the metal ball
The rubber ball suffers greater change in momentum
The metal ball suffers greater change in momentum
Both suffer the same change in momentum

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Physics
Why two thin shirts can keep us warmer than a single thick shirt in winter ?

No radiation of heat takes place
Air layer between two shirts works as good conductor
Two thin shirts become thicker so prevent transmission of heat
Air layer between two shirts behaves like insulating media

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