Oxford PAT 2011, Questions 12 – 16

2011_page9

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6 thoughts on “Oxford PAT 2011, Questions 12 – 16

      1. We’ve been given the equation for the power that is used for cooling and if we plug in the values we get 15 (26 – 6). To work out the power used, just divide by the efficiency which is 30%. This is the same as multiplying by 100 / 30. So you get 15 x 20 x 100 / 30.

      2. Power of light from a star obeys a 1/r² law. The brighter star is twice as far away so its power must be reduced by a factor of 4 when it reaches the eye. So if it looks to have the same brighness it must be emitting 4 times the power.

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