2 What is LIGHT? A type of electromagnetic wave Type of energy that travels as a waveNO medium is requiredWe see things because light reflects off of them
3 What is an Electromagnetic Wave? A transverse waveA wave that can travel through space or matter and consists of changing electric and magnetic fields.Field-a region around an object that can exert a force without actually touching the objectExample:magnetWaves are produced by the vibration and movement of an electron
4 How are Electromagnetic Waves Produced? Produced by the vibration and movement of an electronWhen an electron changes energy levels, energy is emittedThe energy is emitted as a particle called a photonA stream of photons carries the energy from the electron, as a light wave.photon
6 Visible Light We see different wavelengths as different colors When all colors are combined, we see white lightWhen there are no colors, we see black
7 Visible Light Light travels in a straight line When shining a light, closer objects appear brighter, this appears for 3 reasonsThe beam of light spreads outAbsorptionScattering
8 Absorption & Scattering the air particles around the light absorbs (takes) some of the energy from the lightScatteringLight scatters in all directionsThe particles that absorb energy (around the light source) give off light energyThis makes us able to see things near the light that are not on the line that the light is travelingShorter wavelengths scatter more light than longer wavelengths.
9 Law of Reflection Law states that: angle of incidence = angle of reflectionAngle of Light going into surface = angle going outIf the reflecting surface is smooth, then light reflects off of all points at the same angle.If the reflecting surface is rough, then light reflects off at many different angles.
10 LIGHT & COLOR Light can interact with matter in 3 ways TYPES OF MATTER Reflected-light rays reflect at angle of incidenceAbsorbed-energy is transferred to the particlesTransmitted- light passes through the matterTYPES OF MATTERTransparent-light is easily transmittedTranslucent-transmits and scatters lightOpaque-does not transmit any light
11 COLORS of OBJECTSThe color of an object is determined by the wavelength of color that reaches your eye.OPAQUE OBJECTSWhen white light hits a colored object, some colors are absorbed and some are reflectedOnly the light that is reflected reaches your eyes, this is the color that we seeWhite objects REFLECT ALL colorsBlack objects ABSORB ALL colorsTRANSPARENT OBJECTSWe see the color that is transmitted through the matter
12 MIRRORS----- Images in mirrors are reversed left to right Light waves travel in straight lines in all directions from a light sourceAn arrow called a ray can represent the path and direction of the light waveThese rays are used to show the light after it is reflected or refracted- it shows the change of direction
13 Mirrors Reflect Light Mirrors are classified by their shape, plane, concave, and convexThe shape of the mirror affects the way light reflects from it and how an image appears
14 Plane Mirrors A mirror with a flat surface When you look at it, your reflection is upright and the same size as you areImages are reversed from left to rightImage appears to be the same distance from the mirror as in front of itMirrors are opaque, light does NOT travel through themThe image created is virtual-your brain sees the reflected light and thinks it is straight behind the mirror
16 Concave Mirrors Mirrors that are curved inward Form virtual images Can form REAL images-image though which light actually passes, can be projected onto a screenCreate a ray diagram to decide if an image is real or virtual
18 How to Draw Ray Diagrams Draw a ray from the top of the object parallel to the axis. It will reflect and go straight through the focal point.If the distance between the object and the mirror is more than one focal length, draw a ray from the top of the object through the focal point. The ray will reflect parallel to the axis.If the object is less than one focal length away from the mirror, draw a ray though the top of the object from the focal point and it will reflect parallel to the axis.
19 Virtual or REAL?Draw a ray diagram to answer the question, you need to draw two rays from the top of the objectIf the reflected rays cross in front, of the mirror, a REAL image is formedThe crossing point is the top of the imageIf the reflected rays do NOT cross, trace the reflected rays in straight lines behind the mirrorThese lines will cross to show where the image formsThis is a VIRTUAL imageIf the object is placed at the focal point of a concave mirror, NO IMAGE IS FORMED
22 CONVEX MIRRORS A mirror that curves out toward you All images formed are VIRTUAL and UPRIGHT and SMALLER than the original
23 RefractionThe bending of a wave as it passes at an angle from one medium to another.This occurs because the speed of light changes according to the mediumWhen a wave enters a new medium at an angle, the part of the wave that enters first begins to travel at a different speed from the rest of the wave.
24 Refraction and COLORSWhite light is made up of all colors of visible lightEach color has its own wavelengthWhen white light is refracted, the amount that the light bends, depends on the wavelength.Light waves with SHORT wavelengths bend MOREThis allows white light to be separated into different colors during refractionThis is why and how rainbows form
25 Diffraction The bending of waves around barriers or through openings Greatest amount of diffraction occurs when the opening is the same size as the wavelength or smallerLight waves cannot diffract around large obstaclesThis is why you can’t see around cornersLight waves always diffract a small amount
26 Interference When two or more waves overlap Constructive InterferenceResulting wave has a greater amplitude-bright spots of lightDestructive InterferenceResulting wave has a smaller amplitude-dark spots or dim light.
27 Mixing COLORS of LightRED, BLUE and GREEN can be combined in different ratios to produce all colors of visible lightCalled the Primary ColorsWhen they are mixed, they make secondary colorsMixing Colors of PigmentPigment-material that gives a substance color by absorbing colors of light and reflecting othersThis is why we cannot mix red, blue and green paint to make white paint.
28 Lenses Refract LightLens- a curved, transparent object that forms an image by refracting, or bending lightClassified by shapeConvex-thicker in the middle than at the edgesConcave-Thinner in the middle than at the edges
29 Convex Lenses Light is refracted towards the center Light rays enter parallel to axis and are refracted so that they go through the focus pointAmount of refraction and focal length depends on the thickness of the lensLight rays passing through the center of a lens are not refractedCan form REAL AND VIRTUAL images, depends on the focus length and placement of the object