[填空题]
Estimate the time between each photoflajo2puga fs-rngu9 f+ w l)79uy wd314jsh of the applwkv/p1jt9se d7oj 8fsz+u n81e in Fig. 2–18 (or number of photof1zssdwkoj19v jfe8u 7 +/nt8p lashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T = s
flashes per second