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Chapter 15: Sound & Light

Chapter 15: Sound & Light. Section 1 – Sound. Sound carries information about the world to us. Many animals rely on sound to survive. Without sound, the world would be a very dull place. Definition: sound wave– a longitudinal wave caused by vibrations of a medium.

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Chapter 15: Sound & Light

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  1. Chapter 15: Sound & Light Section 1 – Sound

  2. Sound carries information about the world to us. • Many animals rely on sound to survive. • Without sound, the world would be a very dull place. • Definition: sound wave– a longitudinal wave caused by vibrations of a medium. • Sound waves are mechanical waves! Air is the vibrating medium in this example.

  3. The speed of sound depends on the medium: • Sound waves travel faster through liquids and solids than gases. • The speed of sound through air at room temperatureis about 760 mi/h. Dolphins & other marine animals can communicate easily underwater using sound waves.

  4. We hear sounds because of our ear drums… • When sound reaches the ear drum, the sound’s energy is transferred into it. (Law of Conservation of Energy!) • The ear drum vibrates, and allows us to hear the sounds.

  5. The loudness of sound depends on the amount of energy that the sound wave is carrying. • Definition: sound intensity – the loudness of a sound wave. Higher intensity sound waves have larger amplitudes. ROAR! roar!

  6. Intensity is measured in decibels (dB). • The quietest sound that a normal human can hear is 0 dB. • Sounds louder than 120 dB can cause deafness. • Too much energy is transferred into ear drum, and it will burst. Example: A whisper is about 30 dB, a normal conversation is about 60 dB, and a lawnmower is about 90 dB.

  7. The pitch of a sound determines how “high” or “low” it sounds to us. • Definition: pitch – a measure of how high or low a sound is heard. • Pitch depends on sound wave frequency. • High pitched sounds have a high frequency. • Low pitched sounds have a low frequency. • Pitch (frequency) is measured in Hertz, Hz. Low Pitched Sound High Pitched Sound

  8. Humans and animals can hear within certain frequency ranges. • Human beings can hear sounds as low as 20 Hz. • And as high as 20,000 Hz. • Dogs have a hearing range of 40 Hz to 46000 Hz! • Dolphins have a hearing range of 2 kHz – 150 kHz!

  9. Chapter 15:Sound & Light Aurora Borealis: “The Northern Lights” Section 2 – The Nature of Light

  10. What is Light?? • So, if someone asked you that question, what would you say? • Maybe you would say that “Light is energy”. • Or, you might be dumbfounded. Light can be difficult to describe, but there are two descriptions that are used most often.

  11. Light can be described as a waveor as a beam of particles: • Light is an electromagnetic wave that causes electrons to vibrate. • Definition: photon – a particle of light energy that makes up a beam of light.

  12. What is Light?? • Light is the result of energized electrons… • When an electron gains enough energy, it releases that energy as LIGHT • Light can be produced by… • Thermal energy • Chemical energy • Or electrical energy

  13. The main source of light is the sun. • Sunlight is the energy produced by nuclear fusion deep inside the sun. All life on Earth depends on Sunlight!

  14. Auroras • At the north and south poles of the Earth, sunlight creates auroras. • The auroras are produced when sunlight energizes electrons in our atmosphere. • Aurora Borealis – at the north pole. • Aurora Australis – at the south pole.

  15. Ever wondered how fast light travels? • Light is the fastest thing in the universe. • It travels at 186,000 mi/s in a vacuum. That’s MILES per SECOND. • Definition: vacuum – an area where no medium exists. Outer space is a vacuum.

  16. The brightness of light is described by it’s intensity. • Brighter light has a higher intensity (more photons). • High intensity light can, of course, cause blindness.

  17. We have already learned that light is a type of radiation. Light is part of the “electromagnetic spectrum” • Definition: electromagnetic spectrum – the grouping of ALL EM radiation. • EM  Electromagnetic. EMS  Electromagnetic Spectrum. • Visible light is the portion of the EMS that ranges from red to violet.

  18. Chapter 15:Sound & Light Section 3 – The Electromagnetic Spectrum

  19. The Electromagnetic Spectrum • The parts of the EMS: • Radio waves • Microwaves • Infrared rays • Visible light (ROY G. BIV) • Ultraviolet rays • X-rays • Gamma rays • Each of the types of electromagnetic energy have different uses for humans.

  20. The EMS is arranged according to wavelength & frequency. • The waves become stronger as their wavelength becomes shorter.

  21. Radio Waves • Radio waves are the weakest waves on the EMS. • They have the longest wavelength & lowest frequency. • Radio waves are used for communications. • There are AM radio waves… • FM radio waves… • And radio waves used for TV. Frequency: Low Wavelength: Buildings Hazard Rating: Harmless

  22. Microwaves • Microwaves are used for high-power communications, such as satellite & radar. • Microwaves cause water to heat up very quickly, which is how they are able to heat and cook food. Frequency: Low Wavelength: Child Hazard Rating: Minimal

  23. Infrared Radiation (IR) • Infrared radiation (IR) is used for heat-sensing technology. • Satellites & night-vision cameras can detect IR. • Infrared radiation can be felt as “heat”. Frequency: Low Wavelength: Button Hazard Rating: Minimal

  24. Visible Light • Visible light is composed of 7 colors: Red, Orange, Yellow, Green, Blue, Indigo, & Violet Or simply ROY G. BIV Frequency: Medium Wavelength: Bacteria Hazard Rating: Minimal

  25. When light refracts through raindrops, it splits into its 7 colors to form a rainbow!

  26. The primary colors of visible light are… • RED, GREEN, AND BLUE. • When the 3 colors combine, they form white light. • The secondary colors are YELLOW, CYAN, & MAGENTA • They can also be produced with the 3 primary colors.

  27. Ultraviolet Rays • UV light is radiation that is more powerful than visible light. • Earth’s ozone layer blocks out much of the sun’s UV rays. • It is used to sterilize materials. • It can cause severe sunburn! Frequency: High Wavelength: Molecule Hazard Rating: Dangerous

  28. X-Rays • X-rays are the 2nd most powerful form of radiation. • They can pass through skin and flesh. • This is why X-rays are used to take images of bones & tumors in the body & to examine inside objects. Frequency: Very High Wavelength: Atom Hazard Rating: Very Dangerous!

  29. Gamma Rays • Gamma rays are the most powerful form of radiation & have the shortest wavelength. • Gamma rays can destroy living cells. • They are used in medicine to treat cancer & produce images of the body. • The sun emits gamma rays • These are blocked by the magnetic field of the Earth. Frequency: Extremely High Wavelength: Atom Nucleus Hazard Rating: Deadly

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