An optical fibre with refractive index 1.72 is surrounded by a glass coating having refractive index 1.50.find the critical angle for total internal reflection at the fibre-glass interface.

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the design of a ski jumping suit involves a trade-off between giving the skiers lift to get higher jumps and ensuring the skier does not face a lot of drag before the jump itself. an expansive suit may to lift the skier higher, but at the same time, it will also increase the air resistance. higher air resistance as the skier goes down the slope limits the speed of the jump. a big suit also increases the risk of losing balance or control, especially if there's a strong gust of wind. while technologically enhanced suits a lot, clothing is not the only factor in a ski jumper’s success. gathering speed while skiing down the slope, ensuring good speed on the ramp, and maintaining good body posture and form in the air all contribute to a ski jumper's success.

answer a fan shaped mass of sediment deposited at the base of a mountain front do to an abrupt change in stream gradient;