Прочтите текст и напишите ответы на вопросы.

1. What does light consist of? 2. Are radio waves and heat rays visible? 3. What is called photon? 4. What kind of waves can damage human skin? 5. What is called a quantum?

1. Light consists of waves of the same sort as radio waves, infrared rays, ultra-violet waves, X-rays and gamma rays. All these are electromagnetic waves of different wave lengths. Radio waves and heat rays are not visible because they are too long. Xrays and gamma rays are too short to be visible. Light waves are of just the right length to affect our eyes, and so we can see light.
2. As we move down the scale of wave lengths from the very long ones, like radio waves, to the very short ones, like X-rays and gamma rays, we find that they become more and more powerful. Ultra-violet waves are invisible, they are shorter than those of ordinary light waves. That’s why they may be detrimental. They are present in sunlight, but fortunately most of them are stopped by the outer atmosphere of the earth because in large doses they can damage human skin. X-rays and gamma rays
are more dangerous still because of their extremely short wave length. X-rays are so powerful that they can travel through many substances that are opaque to light. They can, for example, pass right through flesh and show up the bones inside.
3. Although light shows many of the properties of waves it also behaves sometimes as if it consisted of little particles, only they are not made of any substance but energy. These little packets of energy are called photons, and the amount of energy in each is called a quantum. There is much more energy in a quantum of X-rays than there is in a quantum of light or radio waves, and this explains why X-rays can damage the body, whereas radio waves have no effect on us.