PHY ch. 7 - 27.1 #12 You are taking pictures of the beach...

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27.1 #12 You are taking pictures of the beach at sunset. Just before the Sun sets, a shutter speed of 1/100 sec at f / 11 produces a properly exposed picture. Shortly after the Sun sets, however, your light meter indicates that the scene is only one quarter as bright as before. (a) If you don’t change the aperture, what approximate shutter speed is needed for your second shot? (b) If, instead, you keep the shutter speed at 1/100 sec what approximate f-stop will be needed for the second shot? Ans. 5.6 Picture the Problem : The light entering your camera has dropped to one-quarter of what is required for proper film exposure. You must either decrease the shutter speed or increase the aperture size in order to maintain the exposure. Strategy: The exposure time should be quadrupled to compensate for the reduced light, which means the shutter speed should be decreased by a factor of four. In part (b), use a ratio of the final aperture area to the initial aperture in order to determine the required f -number for proper exposure if the shutter speed remains the same. Solution:
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PHY ch. 7 - 27.1 #12 You are taking pictures of the beach...

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