Interpreting the Electromagnetic Wave Spectrum

BACKGROUND:

Electromagnetic waves are all around us and range from common light to radio waves and gamma rays. These waves are related to electricity and magnetism in that both sources produce these waves. All substances have a positive and negative side, no matter how big or small they are. Two positives or negatives repel each other, while positives and negatives attract each other. Atomic particles are constantly being hit and deflected. As the world is made up of negatives and positives, energy is constantly being generated. It is like a "bumper car" game. Electromagnetic waves are the consequence of all this bumping. It is difficult to understand this concept, but students need to become familiar with the terms to facilitate their understanding at a later time.

These waves act like the waves we have already seen. Unfortunately, we cannot see the wave motions with our eyes. When an electromagnetic charge is suddenly displaced, a ripple of electric and magnetic force is generated in the same manner in which water ripples are formed by dropping a pebble. Electromagnetic waves, unlike sound (physical) waves can move through a vacuum for they do not require a medium for their existence. They are waves of force.

This activity tries to show the variety of waves that are included in electromagnetic waves. Familiarize students with the terms. Many of your students know about these waves, they just don't connect how they are related.

Radio waves' wavelength are the longest wavelength. On a radio, the channels refer to the frequency. There are two common ways to transmit radio, AM (amplitude modulation) and FM (frequency modulation). Modulation refers to how the wave is varied through its transmission. AM varies its amplitude (strength), while FM varies its frequency.

Television waves have shorter wavelengths than most radio waves. Television is transmitted from distant stations. The television at home picks up these waves and interprets them for us to see. There are UHF and VHF components of television waves.

Microwaves have a higher frequency and as their name suggests, have smaller wavelengths. Microwaves are used not only to cook but also in the communication industry.

Infrared waves are even smaller and are known for their use in detecting heat. A cat's eye can detect infrared light that is why they say a cat sees in the dark. Their eyes detect what human eyes cannot.

Visible light is the spectrum that we are most familiar with. Visible light can be broken into the colors of the rainbow, because each of the colors has a different wavelength and frequency.

Ultraviolet light is known to be harmful to human skin. It is the ozone layer that helps protect us from these rays. However, ultraviolet light can also help kill harmful bacteria.

X-rays are known for their use in viewing inside our body. X-rays can go through soft matter and can outline hard matter. The many uses for X-rays are still not completely known.

Gamma rays and cosmic rays are at the extreme right of the spectrum. Scientists are still trying to unravel their mysterious powers. The rays seem to be very powerful when concentrated, but only the future knows how they will be useful in our society.
PROCEDURE:

Instruct students to use the worksheet to discover the parts of the electromagnetic wave spectrum.

ANSWERS:
1. gamma and cosmic rays.
2. Television and radio waves.
3. Visible light.
4. Sound wave, it is not an electromagnetic wave but a physical wave.
5. Microwave ovens, communications.
6. Broadcasting station
7. Broadcasting station


OBJECTIVES: Interpreting the electromagnetic wave spectrum. Exploring the components of electromagnetic waves. VOCABULARY: frequency gamma rays infrared waves micro waves radio waves ultraviolet waves wave x-rays MATERIALS: worksheet Light Slideshow	Students find the frequency of different components of electromagnetic wave spectrum.