Chapter 5 Notes: Mirrors and Lenses Name: Block:
The Ray Model of Light The ray model of light represents light as a line, or ray, indicating the path of a beam of light. Light travels in straight lines until it strikes something: candle pinhole screen Objects cast a shadow because they block out light rays. The size of the shadow is related to the distance of the object from the light source: solid objects Matter can be classified according to what happens when light energy reaches it: 1) Transparent Allows light to through freely (e.g. air, water, window glass) 2) Translucent Allows most light to get through but is in all directions (e.g. bathroom window glass) 3) Opaque Absorbs and light, preventing any from passing through it (e.g. most objects)
The Law of Reflection The law of reflection predicts the behaviour of reflected light from the surface of a mirror. It states that the angle of equals the angle of. 2 5 6 1 3 4 1) mirror a flat, smooth surface that reflects light 2) an imaginary line that is perpendicular to the boundary between the air and mirror 3) ray an incoming ray that strikes the mirror 4) ray a ray that bounces off the mirror 5) Angle of (θ i ) an angle formed by the incident ray and the normal 6) Angle of (θ r ) an angle formed by the reflected ray and the normal Refraction of Light The angle of refraction is the angle of a ray of light emerging from the boundary between two materials, measured between the ray and the Air-to-Water Boundary when light rays travel to a denser medium they down and refract toward the normal Water-to-Air Boundary when light rays travel to a less dense medium they up and refract away from the normal
Mirrors Mirrors have smooth surfaces that light uniformly. Mirrors can be 1), 2), or 3). All mirrors form an image that has a left-right orientation: 1) Plane Mirrors have a reflective surface that is and smooth. Plane mirrors form an image that appears to be as far behind the mirror as the object is in front of it. Ray Diagram Location (behind or in front of mirror?) Size (smaller or larger than object?) Orientation (inverted or upright?) Type of (real or virtual?)
2) Convex Mirrors have a reflective surface that curves ; they cause light right rays to. The images formed are and than the object. (e.g. security mirrors and rearview and side-view mirrors) Ray Diagram Object far from mirror: Location (behind or in front of mirror?) Size (smaller or larger than object?) Orientation (inverted or upright?) Type of (real or virtual?) Object near mirror:
3) Concave Mirrors have a reflective surface that curves ; they cause light rays to converge. Depending on the distance of the object, a concave mirror can form an image that is inverted or, and can be larger or than the object. (e.g. spotlights, flashlights, lighthouses, car headlights, telescopes and make-up mirrors) Ray Diagram Object located beyond the centre of curvature Location (behind or in front of mirror?) Size (smaller or larger than object?) Orientation (inverted or upright?) Type of (real or virtual?) Objects located at the centre of curvature Objects located between the centre of curvature and the focal point Objects located between the focal point and the mirror
Lenses Lenses are pieces of transparent material that can bend, or, light rays in useful ways to help form a well-focused image. Lenses can be 1) or 2). 1) Concave Lenses are thinner in the middle than the edge; they are used to light rays Ray Diagram Location (behind or in front of lens?) Size (smaller or larger than object?) Orientation (inverted or upright?) Type of (real or virtual?)
2) Convex lenses are thicker in the middle than at the edge; they are used to light rays Ray Diagram The object is located beyond 2F Location (behind or in front of lens?) Size (smaller or larger than object?) Orientation (inverted or upright?) Type of (real or virtual?) The object is located at 2F The object is located between 2F and F The object is located at F The object is located in front of F
Flashcards 1) 2) What is the ray model of light? What is the relationship between the size of a shadow and the distance of the object from the light source? 3) 4) What is a transparent material? What is a translucent material? 5) 6) What is the law of reflection? What is an opaque material? 7) 8) What is the plane mirror? What is the normal?
9) 10) 11) What are the incident ray and the angle of reflection? What are the angle of incidence and angle of reflection? 12) What is the angle of refraction? 13) At which type of boundary do rays slow down and refract toward the normal? 14) At which type of boundary do rays speed up and refract away from the normal? 15) 16) What is a plane mirror? What is a convex mirror? What is a concave mirror?
17) 18) What is a concave lens? What is a convex lens?