Physics
Skating on ice is possible because

The pressure on the ice due to skate raises its melting point
The surface of ice is smooth
Ice is cold
The pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water

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Physics
Purpose of an optical filter is to

Refract light of different colours
Transmit or absorb light of different colours
Reflect lights of different colours
Dispense light into component colours

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