Created by StemPy LabAn astronomical telescope has an objective of focal length and an eyepiece of focal length . It is adjusted so that the final image of a distant star field is formed at the near point of the eye, from the eyepiece. Its magnifying power is ____.
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← A heater coil A brings a pot of water to the boil in 10 minutes when connected to the mains on its own. Another coil B does the same in 15 minutes on its own. If both coils are connected in parallel to the same mains, the same pot of water boils in how many minutes? ____Pure silicon at room temperature has 1.5 × 10¹⁶ free electrons per cubic metre, and the same number of holes. It is doped with 4.5 × 10²² donor (pentavalent) atoms per cubic metre, each of which gives one free electron. If the number of holes per cubic metre in the doped silicon is N × 10⁹, the value of N is ____. →
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