Lasers (part I)

1. Warming up:

What does the word “laser” mean?

2. Look through the following text and give Russian equivalents to the underlined words, word combinations and terms.

Lasers show up in an amazing range of products and technologies. You will find them in everything from CD players to dental drills to high-speed metal cutting machines to measuring systems. They all use lasers.

A n atom, in the simplest model, consists of a nucleus (containing the protons and neutrons) and an electron cloud. It’s helpful to think of the electrons in this cloud circling the nucleus in many different orbits. Although more modern views of the atom do not depict discrete orbits for the electrons, it can be useful to think of these orbits as the different energy levels of the atom. If we apply some energy to an atom, we might expect that some of the electrons in the lower-energy orbitals would transition to higher-energy orbitals farther away from the nucleus, that is go to an excited level. The level of excitation depends on the amount of energy that is applied to the atom via heat, light, or electricity.

This is a highly simplified view of things, but it actually reflects the core idea of how atoms work in terms of lasers. Once an electron moves to a higher-energy orbit, it eventually wants to return to the ground state. When it does, it releases its energy as a photon – a particle of light. You see atoms releasing energy as photons all the time. Anything that produces light does it through the action of electrons changing orbits and releasing photons.

A laser is a device that controls the way that energized atoms release photons. "Laser" is an acronym for light amplification by stimulated emission of radiation, which describes how a laser works.

Although there are many types of lasers, all have certain essential features. In a laser, the lasing medium is “pumped” to get the atoms into an excited state. Typically, very intense flashes of light or electrical discharges pump the lasing medium and create a large collection of excited-state atoms (atoms with higher-energy electrons). Once the lasing medium is pumped, it contains a collection of atoms with some electrons sitting in excited levels.

The excited electrons have energies greater than the more relaxed electrons. Just as the electron absorbed some amount of energy to reach this excited level, it can also release this energy. This emitted energy comes in the form of photons (light energy).

3. Read the text attentively and answer the following questions:

   1. Where can we find lasers?

   2. What is the simplest model of an atom?

   3. What will happen if we apply some energy to an atom?

   4. When is energy as a photon released?

   5. Can we see atoms releasing as photons?

   6. What is “laser”?

4. Use the picture to describe the model of an atom.

5. Describe essential principles of a laser work; use the following words and expressions:

apply; energy; lower-energy orbital; higher-energy orbital; excited level; ground state; release energy; lasing medium; intense flashes of light; electrical discharges; pump; a large collection of excited-state atoms; emitted energy.

6. Retell the text using the following expressions:

The text describes…; According to the text…; The fact is that…; In this case…; In order to…; It turns out that…; One should add...