Science Chap 2

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wave
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A wave is a disturbance that transfers energy from place to place.
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frequency
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Frequency is the number of complete waves that pass a given point in a certain amount of time
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energy
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Energy is defined as the ability to do work
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hertz
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Frequency is measured in units called hertz (Hz)
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medium
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the material through which a wave travels is called a medium
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electromagnetic radiation
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The energy that is transferred through space by electromagnetic waves is called electromagnetic radiation
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crest
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The high point of a wave is called a crest
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trough
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The low point is called a trough
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electromagnetic spectrum
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The electromagnetic spectrum is the complete range of electromagnetic waves placed in order of increasing frequency. Electromagnetic spectrum is made up of: Radio waves Infrared waves Visible light Ultraviolet rays X-rays Gamma rays (RIVU-XG)..order matters longest wavelength to shortest least energy to most energy
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amplitude
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Amplitude is the maximum distance that the particles of the medium carrying the wave move away from their rest positions.
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wavelength
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The distance between two corresponding parts of a wave is its wavelength
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transparent
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A transparent material transmits most of the light that strikes it
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secondary color
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.Two primary colors combine in equal amounts to create a secondary color
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translucent
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A translucent material scatters light
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complementary colors
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Any two colors that combine to form white light are called complementary colors e.g. Yellow/Blue, Cyan/Red, Magenta/Green
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opaque
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An opaque material reflects or absorbs all of the light that strikes it
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pigment
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Colored substances that are used to color other materials. Pigments absorb some colors and reflect others.
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primary colors
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Three colors that can combine to make any other color are called primary colors a) Primary colors of light – RGB (Red, Green, Blue) e.g. Laptop monitor b) Primary colors of Pigments – CMY (Cyan, Magenta, Yellow) e.g. Printer
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reflection
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Reflection occurs when an object or wave bounces back off a surface through which it cannot pass
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optical axis
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Optical axis is an imaginary line that divides a mirror in half
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law of reflection
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a) The law of reflection states that the angle of incidence equals the angle of reflection b) all waves obey this law
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focal point
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The point at which rays parallel to the optical axis meet or converge is called the focal point The location of the focal point depends on the shape of the mirror. The more curved the mirror is, the closer the focal point is to the mirror.
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real image
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A real image forms when rays actually meet.
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plane mirror
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A plane mirror is a flat sheet of glass that has a smooth, silver-colored coating on one side
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convex mirror
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A mirror with a surface that curves outward is a convex mirror.
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image
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An image is a copy of an object formed by reflected or refracted rays of light
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refraction
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Light travels in straight lines if the medium it travels through does not change. If light enters a new medium, it might slow down or speed up, because the speed of light is different for different mediums. If light enters the new medium perpendicular to the boundary, it will keep moving in the same direction. But if it hits the boundary at an angle, it will also bend. This bending of light waves due to a change in speed is known as refraction.
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virtual image
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a)A virtual image is an image you see in a plane mirror b)A plane mirror produces a virtual image that is upright and the same size as the object c)If an object is between the mirror and the focal point, the reflected rays form a virtual image behind the mirror. Virtual images formed by a concave mirror are always larger than the object.
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lens
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A lens is a curved piece of glass or other transparent meterial that refracts light.
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concave mirror
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A mirror with a surface that curves inward like the inside of a bowl is a concave mirror.
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convex lens
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A convex lens or magnifying glass is thicker in the center than at the edges
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concave lens
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A concave lens is thinner in the center than at the edges
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cornea
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The eye’s lens to help focus light rays
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rods
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Contact a pigment that responds to small amounts of light
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pupil
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An opening through which light enters the inside of the eye
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cones
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a) respond to color b) detect red, green , blue (RGB) light c) Respond best in bright light
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iris
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Is a ring of muscle that contracts and expands to change the size of the pupil
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nearsighted
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A nearsighted person can see nearby things clearly, but objects at a distance are blurred
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retina
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Is a layer of cells that lines the inside of the eyeball
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farsighted
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A farsighted person can see distant objects clearly, but nearby objects appear blurry
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camera
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Uses one or more lenses to focus light, and film to record an image The lens of a camera focuses light to form a real, upside-down image on film in the back of the camera
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reflecting telescope
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Uses a large concave mirror to gather light
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telescope
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Forms large images of distant objects Use a combination of lenses or mirrors to collect and focus light from distant objects.
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refracting telescope
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Consists of two convex lenses, one at each end of a tube
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microscope
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Optical tool that makes small objects look larger Uses a combination of lenses to form enlarged images of tiny objects
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electron microscope
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Use a beam of tiny particles called electrons instead of light to produce a magnified image
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objective
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Gathers the light coming from an object and focuses the rays to form a real image
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eyepiece
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Magnifies the image so you can see it clearly
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In what unit is frequency of a wave measured?
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hertz
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How are mechanical waves produced?
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Take a rope…tie one end and move the rope up and down to change the speed, amplitude, frequency and wavelength
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What is an example of a wave that requires a medium? what kind of wave travel without a medium?
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With: waves in the ocean Without: Electromagnetic waves
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What are four basic properties of waves?
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Wavelength Amplitude Frequency Speed (WAFS)
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Use a wave diagram to label the amplitude and wavelength of a wave. In a light wave, which of these properties tells you the color of the light?
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longest wavelength – red shortest wavelength – violet
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Which wave properties are distances? Which properties are measured relative to time?
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Distance – wavelength Time – frequency
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Why can electromagnetic radiation travel through empty space?
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Because they dont need a medium
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List the waves in the electromagnetic spectrum in order from longest wavelength to shortest wavelength. Make sure to include all the colors of visible light.
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Radio waves Infrared waves Visible light >> ROYGBIV Ultraviolet rays X-rays Gamma rays
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Why are some electromagnetic waves harmful to you while others are not?
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Harmful because they mutate our cells Others are harmless because they do not possess the energy to mutate our cells
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List one or more types of electromagnetic waves that are useful for each of these purposes: cooking food, communication, seeing in side the body, curing diseases, reading a book, warming your hands.
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cooking (microwave, infrared) communication(microwave, radio) seeing inside body (xray) curing disease(gamma) reading a book(visible light) warming your hand (infrared)
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What happens when light strikes an opaque material?
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It absorbs or reflects the light
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What colors are used in printing?
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C(Cyan), M(Magenta), Y(Yellow), K(blacK)
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What happens to light that strikes the following materials -clear plastic, aluminum foil and tissue paper?
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clear plastic – transmits (transparent) aluminum foil – reflects (opaque) tissue paper – scatters light (translucent)
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Room darkening window shades are used used to keep sunlight out of a theater. What type of material should be the shades be made of ? Explain.
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Opaque material that reflects or absorbs the sunlight
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What determines the color of an opaque object?
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a) material of the object b) color and brightness of the light
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An actor’s red shirt and blue pants both appear black. What color is the stage light shining on the actor?
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Not red and not blue light
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What are the primary colors of light? The primary colors of pigments?
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RGB – Red Green Blue
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How does the result of mixing the primary colors of pigments compare to the result of mixing the primary colors of light?
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Light / Pigment Mix all colors = White/Black
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Using pigments…what colors combine to make blue?
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Pigment: Magenta + Cyan = blue
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Where does an image in a plane mirror appear to be located?
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Behind the mirror
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Where are convex mirrors typically used?
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car passenger side mirror, banks , grocery stores, parking garages and offices
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Which tends to bend light more – solids or liquids?
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Solid most Liquid less
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What causes a rainbow?
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Sunlight is refracted and reflected by tiny droplets of water Droplets act as prisms and refract white light into colors of the spectrum – red,orange,yellow,green,blue,indigo,violet. Red has longest wavelength and refracts most. Violet has shortest wavelength and refracts least.
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Where does an image form in the eye?
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Forms an upside-down image on the retina
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List the parts of the eye in the order in which light interacts with them
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Cornea – focuses Iris – contracts and expands to change size Pupil – Lens – Retina – forms upside-down image Rods – pigment that responds to light Cones – responds to color Optic nerve – Sends signals from rods & cones to brain to see the light from an object
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How is image formed in the retina?
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After entering the pupil, the light passes through the lens. The lens bends the light to form an upside-down image on the retina.
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What happens to light after it strikes the retina?
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Retina is made of light sensitive cells called rods and cones. Rods and cones detect the color and then change images into signals to that travel to the brain along the optic nerve.
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What types of lenses help correct vision problems?
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Concave lenses correct nearsightedness Convex lenses correct farsightedness
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Describe a nearsighted person’s eye
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Nearsighted person’s eye ball is too long Lens focuses image in front of retina Concave lens in front of eye spreads out the light before they enter the eye, and image forms on the retina.
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With uncorrected vision, where does an image form in a nearsighted person’s eye? In a farsighted person’s eye?
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infront of retina behind the retina
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What part of a camera controls the amount of light that enters the camera?
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The aperture controls the amount of light hitting the film
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flectere (root word)
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to bend
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lux, lucere
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to light
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re-
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back;again
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trans-
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through; across
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mechanical wave
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Mechanical waves are produced when a source of energy causes a medium to vibrate.
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vibration
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A vibration is a repeated back-and-forth or up-and-down motion
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Speed of a Wave
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Speed of Wave = Frequency x Wavelength So u can increase speed by increasing Frequency or Wavelength
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Electromagnetic wave
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a) Transfers electrical and mechanical energy b) Consists of vibrating electric and magnetic fields that move through space at the speed of light
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Radio waves
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a) longest wavelength b) lowest frequency c) used for AM/FM radio and TV signals
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Microwaves
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a) Radio waves with shortest wavelength and highest frequency b) used in microwave oven, cellular phones, radar systems
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Infrared rays
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a) invisible heat b) electric stove, heat lamps
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Visible light
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Red Orange Yellow Green Blue Indigo Violet (ROYGBIV) order matters longest wavelength red 800 nanometers to shortest wavelength violet 400 nanometers
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Ultraviolet rays
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a) wavelength shorter than visible light b) more energy than visible light c) causes skin to produce Vit D…good in small doses d) bad in large doses – skin cancer, damage eyes
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X-rays
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a) wavelength shorter than ultraviolet b) more energy than ultraviolet c) used to produce images of teeth and bones – which absorb X-rays d) bad in large doses – cancer
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Gamma rays
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a) shortest wavelength, greatest amount of energy b) Used in chemotherapy to kill cancer cells
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How to produce electromagnetic waves
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a) All electromagnetic waves are produced by charged particles b) Every charged particle has an electric field around it c) When particle moves it produces a magnetic field d) Electric and magnetic fields at 90 degrees to each other e) When motion of particle changes, magnetic field changes and causes electric field to change f) When one field vibrates, the other field vibrates
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What is the angle between the electric and magnetic fields?
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90 degrees
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Does Electromagnetic waves need a medium?
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No…they can travel through a vacuum e.g. sun’s rays reach Earth traveling through a vacuum
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Speed of electromagnetic waves?
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a) All electromagnetic waves travel at the same speed b) 300,000 km/sec – speed of light c) Light from sun takes 8 mins to reach Earth (150m KM away) d) When light waves (visible light) travels through a medium e.g. Air or Water it slows down
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When visible light hits an object, there can be three outcomes…
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a) light can be reflected b) light can be transmitted c) light can be absorbed
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Color of Light example. Red apple Green leaves a) Green Light b) Red light c) Blue light
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a) Leaves appear green, apple appears black a) Leaves appear black, apple appears red a) Leaves appear black, apple appears black
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What happens to the angle of reflection if the angle of incidence increases?
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The angle of reflection will increase
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Mixing of colors
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When combined in equal amounts, the three primary colors of light produce white light
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Primary Colors of Light
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— Draw Diagram
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Primary Colors of Pigment
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— Draw Diagram
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What if pigments added together – what are the consequences?
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a) Fewer colors of light reflected, more are absorbed. b) The mixture looks darker
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Does an object create a real image or virtual image using a convex lens?
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An object’s position relative to the focal point determines whether a convex lens forms a real image or a virtual image
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Why can a concave lens only form a virtual image?
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A concave lens can produce only virtual images because parallel light rays passing through the lens never meet
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Types of images formed by a convex lens
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a) If an object is farther from the lens than the focal point, a real image forms b) if an object is closer to the lens than the focal point, a virtual image forms
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Which type of lens focuses rays of light? convex or concave?
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Convex
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Describe a farsighted person’s eye
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Farsighted person’s eye ball is too short Lens focuses image behind retina Convex lens in front of eye focuses the light before they enter the eye, and image forms on the retina.

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