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Wave Behaviors

Wave Behaviors. 8-6.4 Summarize the behaviors of waves (including refraction, reflection, transmission, and absorption). Assessment of Prior Knowledge. What happens when a wave strikes an obstacle? What about when it goes right through a material?

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Wave Behaviors

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  1. Wave Behaviors 8-6.4 Summarize the behaviors of waves (including refraction, reflection, transmission, and absorption).

  2. Assessment of Prior Knowledge • What happens when a wave strikes an obstacle? • What about when it goes right through a material? • How does the wave act near the edge of an obstacle?

  3. Refraction Light wave refracting in water • What is refraction? • the bending of waves • What causes refraction? • a change in wave speed as they pass from one medium to another • How does the medium affect wave speed? • As waves pass at an angle from one medium to another, they may speed up or slow down. • The greater the change in speed the more the waves bend.

  4. Air (gas) [slower speed] Change in medium affects speed (waves are bent aka refract) Water (liquid) [faster speed]

  5. CFU • Q. The waves travel faster through the water because ____. a) the air is more dense. b) the water is less dense. c) the water is more dense. d) the air and water have the same density.

  6. The directional change of the light waves occurs because _____. a. light waves travel faster through air than water b. light waves travel faster through water than air c. the angle of reflection of waves always equals the angle of incidence d. waves carrying less energy produce light with lower intensity

  7. Prisms • What do prisms do? • separate/refract white light into its different components or colors • How? • by bending the light at different angles depending on the wavelength of the light passing through the prism. • Different wavelengths of light travel at different speeds in a given medium.

  8. Refraction • In a given medium, different wavelengths of light travel at different speeds

  9. Refraction Hands-On Experiment Now you see it, now you don’t. Oh- there it is again! Materials: Penny Cup Water

  10. Refraction

  11. Lenses • There are two main types of lenses: • convex lenses • concave lenses Convex lenses Concave Lenses

  12. Lenses – An application of refraction • There are 2 basic types of lenses A converging lens (Convex) takes light rays and bring them to a point. A diverging lens (concave) takes light rays and spreads them outward.

  13. Convex Lens • How does a convex lens work? • Convex lens is thicker in the middle than in the edges so it bends light rays together. • When light refracts from air through this type of lens, images appear larger as the light waves bend. • http://www.rkm.com.au/ANIMATIONS/animation-physics-lens-converge.html

  14. Concave Lens • Concave lenses are thinnest in the middle and bend light rays apart, making images appear smaller.

  15. Lens

  16. Ray diagram of magnification of a butterfly, image formed is magnified and virtual A magnifying glass is a convex lens

  17. Practice forming a focal point.

  18. Reflection • What is reflection? • the bouncing back of a wave when it meets a surface or boundary that does not absorb the wave’s energy. • makes images look reversed • What kinds of waves can be reflected? • All types Wave reflecting off smooth flat surface

  19. Reflection • What kind of materials reflect light to form clear images? • Mirrors and other smooth surfaces • A plane mirror is a mirror with a smooth flat surface. • Most bathrooms have a plane mirror.

  20. Reflection

  21. If angle “i” increases slightly, angle “r” will(increase/decrease). increase

  22. Reflection and Luminosity

  23. Demonstrations • http://www.edumedia.fr/a305_l2-plane-mirror.html • http://www.edumedia.fr/a304_l2-plane-mirror-2.html

  24. Mirrors and Lenses

  25. How can you describe the image formed by a plane mirror? • upright and reversed • upright and not reversed • inverted and reversed • inverted and not reversed

  26. Transmission • When are waves transmitted? • when they pass through a given point of medium. • What kind of mediums do sound waves transmit through? • solid, liquid, or gas mediums • What kind of mediums do light waves transmit through? • transparent materials

  27. Translucent, Transparent, Opaque

  28. Transmission:Transparent, Opaque, Translucent • Transparent medium • allow most of light that strikes them to pass through them • The light that is not transmitted is reflected or absorbed • Examples: • Clear windows, colored materials like filters

  29. Transmission:Transparent, Opaque, Translucent • Opaque medium • Allows no light waves to be transmitted through • Example • Wood, stone wall

  30. Transmission:Transparent, Opaque, Translucent • How are translucent materials different? • They let some light through, but they scatter the light in all directions, so that you cannot see clearly through them. • Example: • Tissue paper, wax paper

  31. Identify which is transparent, opaque, and translucent. Comparisons of light transmission1) opaque2) translucent 3) transparent

  32. Absorption • When does absorption of waves occur? • when the energy is not transferred through the given medium or space.

  33. Absorption and Temperature Change • When an object absorbs infrared radiation it becomes warmer because the infrared radiation is transformed to thermal energy. • This causes the particles in the substance to move at a faster rate. How Much Hotter is a Black Shirt that a White One?FABRICS & FIBERS | JESSICA | FEBRUARY 26, 2009 AT 7:57 AMYou may have heard that wearing a black shirt will make you hotter than wearing a white shirt or a lighter colored shirt. This is true because the darker the color of a shirt is, the more light and heat it will absorb into the fabric. It will also heat up far faster than a shirt that is a lighter color.

  34. Behaviors When Waves are Absorbed • The color of an object depends on the light wavelengths that are absorbed and reflected. • If a substance absorbs a certain wavelength of light, it reflects the other wavelengths. • The wavelengths that are reflected are the colors that you see. • Your shirt looks red because the wavelength for red is reflected and all other wavelengths are absorbed. • A color filter allows only certain colors of light to transmit through them.

  35. crest • Label A. • Label B. • What kind of wave? • What is the amplitude? • What is the frequency of the black wave? • Frequency of the red wave? • Which wave (red or black) has more energy? • Why? trough transverse 4 cm 1/8 Hz 1/12 Hz black Shorter wavelength, higher frequency

  36. A 4 cm 2 cm 0 cm -2 cm -4 cm 10 cm 5 cm 0 cm -5 cm B -10 cm

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