英语专业四级听力50篇 20 Waves

How does light get from the sun to the earth? How does music get from the stage to the audience? They move the same way —in waves!

Light and sound are forms of energy. All waves carry energy, but they may carry it differently. Light and sound travel through different kinds of matter. For example, light waves cannot move through walls, but sound waves can. That is why you can hear people talking in another room even though you cannot see hem¹. The energy of some waves is destructive. An arthquake produces seismic² waves.

Catch a wave. Ask a friend to stand a few feet away from you. Stretch a spring between you. Shake the spring to transfer energy to it. What happens? The spring bounces up and down in waves. When the waves reach your friend, they bounce back to you!

Light waves travel 300,000 kilometers (186, 000 miles) per second! They can also travel through a vacuum. That is why light from the sun and distant stars can travel through space to the earth!

1 hem   

n.贴边，镶边；vt.缝贴边；(in)包围，限制

参考例句：

• The hem on her skirt needs sewing.她裙子上的褶边需要缝一缝。
• The hem of your dress needs to be let down an inch.你衣服的折边有必要放长1英寸。

2 seismic   

a.地震的，地震强度的

参考例句：

• Earthquakes produce two types of seismic waves.地震产生两种地震波。
• The latest seismic activity was also felt in northern Kenya.肯尼亚北部也感觉到了最近的地震活动。