1. The beam from a flashlight showed a beggar sleeping at his doorstep.
    借用手电筒的光, 他看到了一个睡在他家门口的乞丐。

2. Hold the flashlight so that the beam shines straight down on a sheet of white paper.
    手握电筒让光线直射在一张白纸上。

3. You can see this for yourself by experimenting with a flashlight.
    你自己用一个手电筒试验一下就会明白。