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A Brief Look at LIGHT Light usually travels only in a straight line. This is known as the ... Law of Rectilinear Propagation Diagrams with Light are referred to as ray diagrams where a ray is a single path followed by light and a beam is a ‘bundle’ of light rays. When light strikes matter – It can be affected in 3 different ways: • Transmitted: light passes through a medium – Ex. Windows • Reflected: light bounces off an object – Ex. Mirrors • Absorbed: light disappears (or certain wavelengths) – Green object all wavelengths of light except green are absorbed Classifying Objects Objects may be classified based on how well they transmit light: Transparent: transmits ALL light Opaque : transmits NO light Translucent: transmits SOME light The Reflection of Light Regular Reflection: this is reflection of light from smooth shiny surfaces. Laws of Reflection Normal Incident Ray Angle of Angle of Incidence Reflection Reflected Ray 90o Mirror Point of incidence Laws of Reflection Normal Incident Ray First Law: The angle of incidence is equal to the angle of reflection Angle of Angle of Incidence Reflection Mirror Reflected Ray Laws of Reflection Normal Incident Ray Second Law: The incident ray, reflected ray, and normal all lie on the same plane Angle of Angle of Incidence Reflection Mirror Reflected Ray Diffuse Reflection Many surfaces appear to be smooth, however when they are viewed under a microscope it is clear they are not. Because of the uneven surface, the light rays are scattered in many directions (diffused). Diffuse Reflection Further examination of a irregular surface show that they too obey the laws of reflection (ie. Angle of incidence = angle of reflection). Diffuse Reflection Most objects are made of rough surfaces (and therefore scatter light); if this did not happen, indoor lighting would not be effective. – ie. Walls, floors, ceilings, etc. scatter light in all directions, making them visible. Time to practice! Complete the worksheet “kinds of reflections” Complete the worksheet “regular and diffuse reflection” Read text p.479-481 and p.484-486 Do Questions: p. 481 #3, 5, p. 486 #1-5 Optical Images An image is the representation of an object formed by the interaction of light rays. Characteristics (LOST): Location: behind or in front of mirror Orientation: vertical (upright or inverted) lateral (left to right) Size: bigger, smaller or same size as object Type : Real – when the reflected rays converge in front of the mirror to produce an image (can be seen on a screen) or Virtual – when the reflected rays converge behind the mirror (cannot be reflected onto a screen) Images Formed in Plane Mirrors Mirror How do I see an image of the arrow?? Images Formed in Plane Mirrors Mirror Light from the arrow hits the mirror Images Formed in Plane Mirrors Mirror ..and is reflected into my eye Images Formed in Plane Mirrors Mirror ..and my brain ‘sees’ the image where the light appears to have come from! The image!! Characteristics of a PLANE MIRROR Image Characteristics in a plane mirror are always: Location: behind the mirror the same distance from the mirror as the object Orientation: image is upright, and laterally inverted Size: same size as object Type : virtual (In you book it’s SALT (Size, Attitude, Location, Type)) Homework Time! Complete Worksheet “Plane Mirrors and their Images” Complete Worksheet “Drawing Images in a Plane Mirror” Read pg. 488-492 Do Questions pg. 493 #1-7, 9 REMINDER: QUIZ on Tuesday!!! (electromagnetic spectrum, sources of light, law of reflection and images in a plane mirror)