在练习射击时，要“三点一线”才能射得准，即枪上标尺缺口、枪上的准星和射击目标要重合，这是根据______的原理．生活中利用这一原理的现象还有很多，例如：______．
（1）击中的“三点”指的是：枪口上的缺口、靶心、眼睛，根据光沿直线传播的原理，当三点一线时，可以瞄准靶心，有利于提高射击成绩；
（2）生活中还有很多现象时利用了光的直线传播，例如：影子的形成；日食月食的形成；小孔成像；
故答案为：光的直线传播；手影的形成、日食月食的形成，小孔成像．
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| My name is Lily. My father is a teacher. His students love him a lot because he is funny. I love him, too, but I think he can be "foolish" 1 . Once we moved into a new house and had to go shopping to buy new chairs and lights. In the supermarket, I'm interested 2 some of the beautiful lights with good qualities and made my father buy them. When we got home, my father began to work out how much money we had 3 that day. Suddenly, he stopped."Something's wrong." he said."I've got 30 yuan 4 than I should!""That's great," I said."You can buy me that 5 book I want." Father said nothing. Instead, he counted (数) how much money he had again and again. "The salesgirl must have made a mistake. We 6 go back to the shop," he said. "Do you have to go back?" I asked. "Nobody will know we 7 too much change (找零). It would be foolish to go back." "It wouldn't be 'foolish'." my father said angrily. "It's called being 8 ." At that moment, I looked into his eyes and knew he was right. The salesgirl was surprised to see us in the shop again. But 9 we gave her the money, she thanked us a lot. On my way home, my father stopped me 10 smiled."Do you still want that cartoon book?" he asked. I looked at my "foolish" father and answered loudly, "Father, you are the greatest!" | ||||
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