Sound PS-7.6: summarize reflection and interference of both sound and light waves and the refraction and diffraction of light waves PS-7.7: explain the Doppler effect conceptually in terms of the frequency of the waves and the pitch of the sound

Sound Waves ◦ compression mechanical wave ◦ Requires a medium ◦ Can be produced by vibrating objects ◦ Reflects  Produces echoes off hard surfaces

Sound Waves What is interference? What does it mean to have constructive interference? Destructive? How does interference affect sound? ◦ Destructive interference makes sounds quieter ◦ Constructive interference makes sounds louder

Properties of Sound Intensity ◦ The amount of energy that flows through a certain area in a specific amount of time ◦ a large intensity will make the wave travel farther ◦ A wave with a small amount of intensity will not travel as far ◦ As the distance increases, the intensity decreases Loudness ◦ The human perception of sound intensity

Properties of Sound Doppler Effect ◦ The change in pitch or wave frequency due to a moving wave source ◦ Occurs when a wave source is moving towards an observer or away from the observer ◦ There is no shift when the source and observer are not moving toward or away from each other

Light Waves Light waves ◦ Electromagnetic waves ◦ Reflect, refract, and diffuse ◦ Can interfere constructively and destructively

Light Waves Reflection ◦ Law of reflection says ‘the angel of incidence is equal to the angle of reflection

Light Waves Reflection in Plain Mirror ◦ Image appears as far behind the mirror as the object is in front of it ◦ The image and the object appear to be the same size ◦ Image is upright

Light Waves Refraction ◦ Change direction upon entering another medium in which the waves travel at different speeds ◦ Ex: prism

Light Waves Diffraction ◦ Bending of a wave around a barrier Interference ◦ Creates areas of light and dark  Amplitude is observed as brightness  Darker areas show destructive interference ◦ Can also create color pattern  Destructive interference- no color seen  Constructive interference- color

Light Waves Lenses ◦ Concave (diverging) ◦ Convex (converging)