WAVES

1. WAVES 8th Grade Pre-AP Science Notes

2. Key Terms: • Waves: A disturbance that transfers energy from place to place. • Amplitude: the height of a wave; the distance from the middle of a transverse wave to the crest or trough.

3. Key Terms: • Wavelength: the distance from one wave top, or crest, to the next. • In transverse waves – distance between two crests or troughs • In longitudinal waves – distance between two compressions or rarefactions

5. Key Terms: • Frequency: the number of waves that pass a point in one second: • Long wavelengths have low frequencies • Short wavelengths have high frequencies

6. Key Terms: • Rarefaction: is the name given to the region where the coils of the spring are pulled apart. • Compression: is the name given to the region where the coils of the spring are pushed together .

8. Waves transmit energy without transmitting matter • This means that waves can move energy from one place to another without moving any matter from one place to another . • The amount of energy a wave has depends on its amplitude .

9. Wave notes • Most waves move through media (matter) but only move backwards and forwards (longitudinal) or side to side (transverse) while the wave passes.

10. Wave notes: • After the wave has gone, the matter is back where it started but energy has been carried by the wave from its origin (where it begins) to its destination (where it finishes).

11. Wave notes: • One type of wave (electromagnetic) does not need any media (matter) to get it from its origin to its destination . It can travel through a vacuum (nothing) so these waves can travel from our sun or other stars toEarth and other planets through space.

12. 3 Types of Waves: • 1. Mechanical • 2. Electromagnetic • 3. Matter

13. Mechanical waves: • Mechanical waves require a material (medium) through which to travel. (air, water, ropes) • These waves are divided into 3 different types.

14. 3 types of mechanical waves: • Transversewaves cause the medium to move perpendicular to the direction of the wave. • Longitudinalwaves cause the medium to move parallel to the direction of the wave. • Surface waves are both transverse waves and longitudinal waves mixed in one medium.

15. Electromagnetic waves: • Do not require a medium to travel. Examples of electromagnetic waves are light waves and radio waves.

16. Matter waves: • Are produces by electrons and particles.

17. Radio Waves AM and FM

18. AM Radio Waves • AM stands for amplitude modulation • On AM broadcasts, the frequency of the wave remains constant. • AM frequencies range from 535 kHz to 1605 kHz. • These radio waves vibrate at frequencies ranging from 535-1,605 thousand times per second.

19. AM Radio Waves • Have relatively long wavelengths and are therefore easily reflected by Earth’s Ionosphere. • The Ionosphere is an electrically charged layer high in the atmosphere. • This is why AM radio stations can broadcast over long distances compared to FM radio stations.

20. AM Radio Waves: diagram • Draw diagram on board.

21. FM Radio Waves • FM stands for frequency modulation. • On FM broadcasts, the amplitude of the wave remains constant. • FM signals travel as changes, or modulations, in the frequency of the wave. • FM stations broadcast at frequencies from 88 MHz to 108 MHz. • FM radio waves vibrate from 88 million to 108 million times each second.

22. FM Radio Waves • have higher frequencies and more energy than AM waves. • penetrate the atmosphere (instead of being reflected back to Earth like AM waves). • For this reason, FM waves do not travel as far as AM waves. • are usually received clearly and produce a better sound quality than AM waves • are generally used to broadcast music.

23. Cellular Telephones • Cell Phones transmit and receive signals using high frequency radio waves or microwaves. • The cellular system works over regions divided into many small cells. • Each cell has its own transmitter and receiver. • Cell phone signals cannot travel great distances • They are only strong enough to reach a few nearby cells.

24. Communications Satellites Satellite Telephone System Television Satellites The Global Positioning System Satellite Radio Amateur Radio Satellite Internet (Broadband)

25. Communication Satellites • are remote controlled spacecraft that orbit the Earth. • Because electromagnetic waves travel in straight lines, they cannot curve around Earth. • Satellites receive signals from Earth and transmit them to other parts of the world.

26. Global Positioning System • Originally designed by the US Military • Uses a group of 24 communication satellites that work together by broadcasting radio signals to and from Earth. • Uses signals from at least 3 satellites at a time to determine exact location on Earth.