Physical Science Chpts. 18, 19, 20 Short version Light Sound Waves Mirrors Lenses

Chapter 18 Waves Rhythmic disturbances that carry energy through matter or space Medium Material through which a wave transfers energy can be gas, liquid or solid

Wave Types Transverse waves Medium moves at right angles to direction of the wave travels Page 499 picture of wave Wavelength Distance between a point on one wave and the identical point on the next wave

Wave Types Transverse Troughs Lowest point on a wave Crest Highest point on a wave Amplitude Distance from the crest or trough of a wave to the rest position of the medium

Wave Types Velocity of a wave Mathematical Velocity equals wavelength times frequency

Wave Types Compressional Waves Matter vibrates in the same direction as the wave travels Sound waves Page 506 picture of wave Like a slinky in movement

Wave Types Compressional waves Wavelength is equal to one compression and one rarefraction Compression Squeezed together Dense area of wave Rarefraction Less dense area of a wave

Wave Types Compressional waves Sound Pitch Highness or lowness of a sound Depends on frequency of the wave High frequency— higher pitch Loudness Is the human perception of sound intensity Higher the intensity and amplitude the louder the sound

Wave Types Compressional Waves Intensity Depends on amount of energy a wave has Intensity increases as amplitude increases

Chapter 19 Light Electromagnetic radiation Transverse waves Radiate from particles Transfer of energy Pg 529 electromagnetic spectrum

Light Photons Tiny particles, like bundles of radiation Radio waves—listening Microwaves—cooking Infrared—slightly longer wavelength than visible light—heat Visible radiation—ROY G BIV Red, orange, yellow, green, blue, indigo, violet

Light Ultraviolet—kills cells X-rays—medical uses Gamma Rays—most penetrating of all waves—kills cells Ozone—3 oxygen molecules combined— protect Earth by filtering UV radiation

Light Opaque Material Absorb or reflect all light Cannot see through the material Transparent Material Allow light to pass through You can clearly see through them Translucent Material Allow light to pass through You cannot clearly see objects Wax paper

Colors Light reflected back is the color you see Red longest wavelength Violet shortest wavelength of the colors

Colors Pigment Colored material that absorbs some colors and reflects other colors

Light Incandescent Light Produced by a thin wire called a filament Loses heat energy Fluorescent Light Produces light without excessive loss of thermal energy

Light Reflection Occurs when a wave strikes an object and bounces off Law of Reflection The angle of incidence is equal to the angle of reflection page 546

Light Refraction Bending of waves caused by a change in their speed when moving in different mediums Diffraction The bending of waves around a barrier Diffraction grating A piece of glass or plastic made up of many parallel slits

Chapter 20 Mirrors and Lenses Plane Mirror Mirror with a flat surface Piece of glass with a reflective coating on front and back

Virtual Image An image in which no light rays pass through the image

Mirrors Concave Mirrors Page 559 Concave lenses Thinner in the middle Enlarges and flips images upside down Convex Mirrors Page 559 Convex lenses are thicker in the middle than the edges Always virtual image, upright and smaller Vision page 566