Wave types

 

A wave is a disturbance that propagates through empty space or a medium such as air or water, usually transporting energy as it travels.

In «transverse waves», the disturbance is at right angles to the wave's direction of motion. Electromagnetic radiation, including visible light, is a form of transverse wave in which magnetic and electric fields oscillate at right angles to the wave’s direction of travel. In «longitudinal waves», the disturbance is parallel to the wave's direction. These include sound waves in gases and liquids. Water waves are an example of a wave that is both transverse and longitudinal - a floating cork will move in a circle as a wave washes past it.

Waves are characterized by their wavelength (the distance between peaks or compressions], frequency (the rate at which waves pass a given point and amplitude or intensity. Standing or stationary waves occur when waves are held in a fixed position - for instance, when a guitar string vibrates. Such waves always involve a whole or half-number of waves, and hence the length of the string determines the wavelengths it can maintain.

 

How Does a Radio Work?

The space around you may look empty—but it isn’t. At all times it is filled with radio frequency waves from nearby radio stations. They are causing minute vibrations in all the metal objects in the room. But you can hear these vibrations only if you turn on your radio. Your radio picks up the radio waves of the station you want to hear and turns them into sound waves. How does it do this?

1. Your radio’s antenna (or aerial wire) picks up all the radio frequency currents that are in the air around it.

2. The tuner selects the frequency of the desired station and blocks out the frequencies of other stations.

3. Now your radio separates the program current from the carrier current. Electronic devices block off the carrier current so that only the program current is left.

4. The program current, which is very weak, must be amplified until it can operate the loudspeaker. This is done by transistors.

5. The loudspeaker changes the program current into sound waves. These sound waves are a copy of those in the broadcasting studio.

2. In pairs ask and answer your questions.

3. Draw a.«longitudinal wave», b.«transverse wave» in your copybooks.

 

 

a. …………………………………………………………..

 

 

b. …………………………………………………………..

 

 

4. Word search

1. What eleven-letter plural noun in the reading means «tiny electronic devices made from semiconductors that control the flow of electrical current»? ___________________________

2. What eight-letter plural noun in the reading means «places with electronic equipment for sending out radio or TV programs»__________________________

3. What five-letter adjective in the reading means «made of a chemical— such as iron, gold, or aluminum—that conducts electricity»? ___________________________

 

5. Circle a letter to show the antonym of the boldface word in each sentence.

1. Nearby radio stations fill the air around you with radio frequency waves.

a. overlapping b. faraway c. powerful

2. In order to operate the loudspeaker, the program current must be amplified.

a. ignited b. refined c. silenced

3. The tuner selects the frequency of the desired station.

a. best b. unwanted c. chosen

4. The space around you is never empty.

a. quiet b. occupied c. hollow

6. In a different context, the same word can be a different part of speech. Notice how the boldface words from the reading are used in each sentence. Then identify the part of speech by writing noun, verb, or adjective.

1. ____________________ Is that information current or out-of-date?

2. ____________________ Will you take a minute to answer my question?

3. ____________________ Ed programs his computer to do specialized tasks.

4. ____________________ The TV programs I like are on Tuesday night.

5. ____________________ Minute particles of dust covered the furniture.

6. ____________________ The North Atlantic current moves across the ocean from Newfoundland to England.

7. Study definitions, read and translate the examples:

Current - a flow of electric charge or the rate of that flow.

E.g. When the magnet and the wire move near each other, an electric current passes through the wire.

Electricity - a fundamental form of kinetic, or potential, energy created by the movement of charged particles, such as electrons.

E.g. In 1831, a former bookbinder named Michael Faraday proved that a magnetic field could create electricity.

Electromagnet - a core of magnetic material surrounded by a coil of wire through which an electric current is passed to magnetize the core.

E.g. Electromagnets are used in doorbells, loudspeakers, electric motors, and to lift large amounts of magnetic materials, such as scrap iron.

Magnetism - the phenomenon of physical attraction for iron observed in magnets, inseparably associated with moving electricity and characterized by fields of force

E.g. Scientists have figured out how to create magnetism with electricity by running an electric current through loops of wire.

 

 

8. Give definitions to the following and use these words in different contexts:

 

1. Wavelength -

2. Frequency-

3. Amplitude-

4. Entropy -

5. Generator –

 

9. In your own words explain how telegraph works.