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The propagation speed of sound and light in the air is about 340m / s and 3 × 108m / s respectively. In the 100 meter race, if the timekeeper starts to count when he hears the starting gun, the time of counting is longer than the actual running time of the athlete______ (choose "more" or "less")______ s．
The speed of sound transmission is 340m / s, and it takes a certain amount of time for the sound to reach the timekeeper from the sound of the gun. When the timekeeper hears the sound of the gun and counts again, the athlete has run a certain distance, so the recorded time is less than the actual time; ∵ v = st, ∵ the time that the timekeeper counts less is the time that the sound passes 100m: T = SV = 100m340m / s ≈ 0.29s
Two examples of application light propagating along a straight line are given
Pinhole imaging
The formation of shadow
solar eclipse
The role of analogy in the development of Physics
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When we learn some very abstract physical quantities that can not be seen or touched, because it is not easy to understand, we take out a quantity that can be seen and is very similar to it for comparative study
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