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  1. Objectives Recognize what factors affect the speed of sound. Relateloudness and pitch to properties of sound waves. Explain how harmonics and resonance affect the sound from musical instruments. Explain how sonar and ultrasound imaging work. Section 1 Sound Chapter 15

  2. Properties of Sound A sound waveis a longitudinal wave that is caused by vibrations and that travels through a material medium The speed of sound depends on the medium. The speed of sound in a particular medium depends on how well the particles can transmit the compressions and rarefactions of sound waves. Sound waves travel faster through liquids and solids than through gases. Section 1 Sound Chapter 15

  3. Section 1 Sound Chapter 15 Properties of Sound, continued • Speed of Sound in Various Mediums

  4. Section 1 Sound Chapter 15 Speed of Sound

  5. Properties of Sound, continued Loudness is determined by intensity. The intensityof a sound wave describes the rate at which a sound wave transmits energy through a given area of the medium. Intensity depends on the amplitude of the sound wave as well as your distance from the source of the waves. Section 1 Sound Chapter 15

  6. Section 1 Sound Chapter 15 Sound Intensity and Decibel Level

  7. Properties of Sound, continued Pitch is determined by frequency. Thepitchis a measure of how high or low a sound is perceived to be depending on the frequency of the sound wave. A high-pitched sound corresponds to a high-frequency, and a low-pitched sound corresponds to a low frequency. Section 1 Sound Chapter 15

  8. Section 1 Sound Chapter 15 Pitch

  9. Properties of Sound, continued Humans hear sound waves in a limited frequency range. Any sound with a frequency below the range of human hearing is known as an infrasound. Aninfrasoundis slow vibrations of frequencies lower than 20 Hz. Any sound with a frequency above human hearing range is known as an ultrasound. Anultrasoundis any sound wave with frequencies higher than 20 000 Hz. Section 1 Sound Chapter 15

  10. Section 1 Sound Chapter 15 Comparing Infrasonic and Ultrasonic Sounds

  11. Musical Instruments Musical instruments rely on standing waves. Standing waves can exist only at certain wavelengths on a string. The primary standing wave on a vibrating string has a wavelength that is twice the length of the string. The frequency of this wave is called the fundamental frequency. Section 1 Sound Chapter 15

  12. Section 1 Sound Chapter 15 Fundamental Frequency

  13. Musical Instruments Harmonics give every instrument a unique sound. Certain whole-number multiples of the fundamental frequency are called harmonics. Every musical instrument has a characteristic sound quality resulting from the mixture of harmonics. Instruments use resonance to amplify sound. Resonanceisa phenomenon that occurs when two objects naturally vibrate at the same frequency. Section 1 Sound Chapter 15

  14. Section 1 Sound Chapter 15 Resonance (Frequency)

  15. Sonar, sound navigation andranging, is a system that uses acoustic signals and echo returns to determine the location of objects or to communicate. Sonar is used for underwater location. A sonar system determines distance by measuring the time it takes for sound waves to be reflected back from a surface. d = vt d is distance v is theaverage speed of the sound waves in water t is time Section 1 Sound Chapter 15 Ultrasound and Sonar

  16. Ultrasound imaging is used in medicine. The echoes of very high frequency ultrasound waves are used to produce computerized images called sonograms. Some ultrasound waves are reflected at boundaries. How much sound is reflected depends on the density of the materials at each boundary. Section 1 Sound Chapter 15 Ultrasound and Sonar

  17. Section 1 Sound Chapter 15 Sonar

  18. Objectives Recognize that light has both wave and particle characteristics. Relatethe energy of light to the frequency of electromagnetic waves. Describedifferent parts of the electromagnetic spectrum. Explain how electromagnetic waves are used in communication, medicine, and other areas. Section 2 The Nature of Light Chapter 15

  19. Waves and Particles The two most commonly used models describe light either as a wave or as a stream of particles. Light can be modeled as a wave. This model describes light as transverse waves that do not require a medium in which to travel. Light waves are also called electromagnetic waves because they consist of changing electric and magnetic fields. Section 2 The Nature of Light Chapter 15

  20. Waves and Particles, continued The wave model of light explains much of the observed behavior of light. Light waves may reflect, refract, or diffract. Light waves also interfere with one another. The wave model of light cannot explain some observations. When light strikes a piece of metal, electrons may fly off the metal’s surface. Section 2 The Nature of Light Chapter 15

  21. Waves and Particles, continued Light can be modeled as a stream of particles. In the particle model of light, the energy of light is contained in packets called photons. Aphotonisa unit or quantum of light. A beam of light is considered to be a stream of photons. Photons do not have mass. Section 2 The Nature of Light Chapter 15

  22. Section 2 The Nature of Light Chapter 15 The Dual Nature of Light

  23. Waves and Particles, continued The model of light used depends on the situation. The energy of light is proportional to frequency. The speed of light depends on the medium. Section 2 The Nature of Light Chapter 15

  24. Section 2 The Nature of Light Chapter 15

  25. Section 2 The Nature of Light Chapter 15 Energy of a Photon

  26. Waves and Particles, continued Section 2 The Nature of Light Chapter 15 • The brightness of light depends on intensity. • Intensityis the rate at which energy flows through a given area of space. • Like the intensity of sound, the intensity of light from a light source decreases as the light spreads out in spherical wave fronts.

  27. Section 2 The Nature of Light Section 2 The Nature of Light Chapter 15

  28. The Electromagnetic Spectrum, continued Infrared (IR) light can be felt as warmth. Microwaves are used in cooking and communication. Radio waves are used in communications and radar. Air-traffic control towers use radar to determine the locations of aircraft. Radar, radio detection and ranging Section 2 The Nature of Light Chapter 15

  29. The Electromagnetic Spectrum , continued The electromagnetic spectrum consists of light at all possible energies, frequencies, and wavelengths. Sunlight contains ultraviolet light. The invisible light that lies just beyond violet light falls into the ultraviolet(UV) portion of the spectrum. X rays and gamma rays are used in medicine. Section 2 The Nature of Light Chapter 15

  30. Section 2 The Nature of Light Chapter 15 Electromagnetic Spectrum

  31. Section 2 The Nature of Light Chapter 15 Electromagnetic Spectrum

  32. Section 3 Reflection and Color Chapter 15 Objectives • Describe how light reflects off smooth and rough surfaces. • Explain the law of reflection. • Show how mirrors form real and virtual images. • Explain why objects appear to be different colors. • Describe how colors may be added or subtracted.

  33. Section 3 Reflection and Color Chapter 15 Reflection of Light • Light can be modeled as a ray. • Alight ray a line in space that matches the direction of the flow of radiant energy. • This model is used to describe reflection and refraction. • Using light rays, one can trace the path of light in geometrical drawings called ray diagrams.

  34. Section 3 Reflection and Color Chapter 15 Reflection of Light, continued • Rough surfaces reflect light rays in many directions. • Such reflection of light into random directions is called diffuse reflection. • Smooth surfaces reflect light rays in one direction

  35. Section 3 Reflection and Color Chapter 15 Reflection of Light, continued • Thelaw of reflection states that the angle of incidence equals the angle of reflection. • On smooth surfaces, the angle of the light rays reflecting off the surface is called the angle of reflection. • Theangle of incidence is the angle of the light rays striking the surface.

  36. Section 3 Reflection and Color Chapter 15 • When light hits a smooth surface, the angle of incidence () equals the angle of reflection ( ′).

  37. Section 3 Reflection and Color Chapter 15 Law of Reflection

  38. Section 3 Reflection and Color Chapter 15 Mirrors, continued • Areal image an image of an object formed by light rays that actually come together at a specific location. • A real image results when light rays from a single point of an object are focused onto a single point or small area. • Usually the image is upside down.

  39. Avirtual imageis an image that forms at a location from which light rays appear to come but do not actually come. • Images are usually right side up.

  40. Section 3 Reflection and Color Chapter 15 Comparing Real and Virtual Images

  41. Section 3 Reflection and Color Chapter 15 Mirrors • Flat mirrors form virtual images by reflection. • Avirtual imageis an image that forms at a location from which light rays appear to come but do not actually come.

  42. Section 3 Reflection and Color Chapter 15 Mirrors, continued • Curved mirrors can distort images. • Mirrors that bulge out are called convex mirrors. • Indented mirrors are called concave mirrors. • Concave mirrors can create real images. • Concave mirrors are used to focus reflected light. • A concave mirror can form a virtual image behind the mirror or a real image in front of the mirror.

  43. Section 3 Reflection and Color Chapter 15 Comparing Concave, Convex and Plane Mirrors

  44. Section 3 Reflection and Color Chapter 15 Seeing Colors • The different wavelengths of visible light correspond to many of the colors that you perceive. • Objects have color because they reflect certain wavelengths. • Colors may add or subtract to produce other colors.

  45. Section 3 Reflection and Color Chapter 15 Subtractive primary colors Additive primary colors Red, green, and blue lights can combine to produce yellow, magenta, cyan, or white. Yellow, magenta, or cyan filters can combine to produce red, green, blue, or black.

  46. Section 3 Reflection and Color Chapter 15 Additive Color Mixing

  47. Section 4 Refraction, Lenses, and Prisms Chapter 15 Objectives • Describe how light is refracted as it passes between mediums. • Explain how fiber optics use total internal reflection. • Explain how converging and diverging lenses work. • Describe how prisms disperse light and how rainbows form.

  48. Section 4 Refraction, Lenses, and Prisms Chapter 15 Refraction of Light • Light waves bend, or refract,when they pass from one medium to another. • Light bends when it changes mediums because the speed of light is different in each medium.

  49. Section 4 Refraction, Lenses, and Prisms Chapter 15 Refraction

  50. Section 4 Refraction, Lenses, and Prisms Chapter 15 Refraction