【英语时差8,16】鹰的眼睛（上）

An eagle circling three hundred feet in the air looks to us like a dot in the sky. But even from that height, the eagle is scanning the ground for prey¹. To help them see small objects from a distance, birds eyes produce a telephoto effect by combining two lenses in much the same way that Galileo combined glass lenses to build some of the earliest telescopes. Light entering our eyes passes through a tiny lens in the front of the eye and is then projected, like a slide in a slide projector², on the retina in the back of the eye. In humans, the surface of the retina is smooth, like a movie screen and so the objects at the edge of our vision appear the same size as objects at the center. In a bird’s eye, a small pit on the surface of the retina acts as a second lens to enlarge a portion of the image.

1 prey   

n.被掠食者，牺牲者，掠食；v.捕食，掠夺，折磨

参考例句：

• Stronger animals prey on weaker ones.弱肉强食。
• The lion was hunting for its prey.狮子在寻找猎物。

2 projector   

n.投影机，放映机，幻灯机

参考例句：

• There is a new projector in my office.我的办公室里有一架新的幻灯机。
• How long will it take to set up the projector?把这个放映机安放好需要多长时间？