Light 1.pptx
- 1. Properties of Light summary 1) Light doesn’t need medium to propagate (electromagnetic wave) 2) Light propagates as a transverse wave 3) Light travels in straight lines 4) Light travels much faster than sound 5) We see things because they reflect light into our eyes 6) Shadows are formed when light is blocked by an object
- 2. Reflection Reflection from a mirror: Incident ray Normal line Reflected ray Angle of incidence Angle of reflection Mirror
- 3. The Law of Reflection Angle of incidence = Angle of reflection In other words, light gets reflected from a surface at ___ ______angle it hits it. the same!
- 4. Clear vs. Diffuse Reflection Smooth, shiny surfaces have a clear reflection: Rough, dull surfaces have a diffuse reflection. Diffuse reflection is when light is scattered in different directions
- 5. Using mirrors Two examples: 1) A periscope 2) Car lamp
- 6. Examples of light reflection 60° 70° 2nd reflector Incident ray Determine the angle of reflection on 2nd reflector!
- 7. The Formation of Images by a Plane Mirror Your image in a flat mirror has four properties: 1. It is upright. 2. It is the same size as you are. 3. The image is as far behind the mirror as you are in front of it. 4. It is reversed, left <--> right The person’s right hand becomes the image’slefthand. Emergency vehicles are usually reverse-lettered so the lettering appears normal in the rear view mirror of a car.
- 8. The Formation of Images by a Plane Mirror A ray of light from the top of the chess piece reflects from the mirror. To the eye, the ray seems to come from behind the mirror. Because none of the rays actually emanate from the image, it is called a virtual image. Each point of an illuminated object emits a continuum of light rays in a range of directions. Two of these rays are shown here.
- 9. The Formation of Images by a Plane Mirror The geometry used to show that the image distance di is equal to the object distance do. Since by intersecting lines, Thus ABC and BCD are similar triangles. Since the triangles share the common side BC, they are also identical triangles, so do = di
- 10. observer Plane mirror object image So Si So = Si i r i = r i r
- 11. Plane mirror observer Wall object image Will the observer be able to see all the image completely inside the mirror ?
- 12. The Formation of Images by a Plane Mirror Conceptual Example 1 Full-Length Versus Half-Length Mirrors What is the minimum mirror height necessary for her to see her full image? Start with a mirror which is exactly her height. Based on this reflection, the length of the plane mirror required to see her full image is only half of her body height.
- 13. The Formation of Images by a Plane Mirror Conceptual Example 2 Multiple Reflections A person is sitting in front of two mirrors that intersect at a right angle. The person sees three images of herself. Why are there three, rather than two, images? 𝒏 = 𝟑𝟔𝟎° 𝜽 − 𝟏 Where: n = number of images formed θ = angle between two mirrors
- 14. Spherical Mirror Reflection on Concave and Convex Mirror