Spherical Mirrors Alfano I: Year 4
Concave Mirrors Concave mirrors are a type of spherical mirrors. We see them used as make-up mirrors or shaving mirrors, and today we are going to learn why. The principle of reflection still holds; the way in which light is reflected in these cases is made more interesting by the spherical geometry.
Convex Mirrors Convex mirrors are a type of spherical mirrors. We see them used on streets or in stores.
Ray Diagrams Parallel Ray: Parallel to optic axis. Reflected through focal point. Chief Ray: Passes through center, hits mirror perpendicular and returns through center. Focal Ray: Passes through the focal point, reflected parallel to optical axis. Need 2 of these rays to locate the virtual image.
Equations 1 + 1 = 1 do di f m = hi = -di ho do spherical mirror equation: 1 + 1 = 1 do di f magnification: m = hi = -di ho do
Practice! For a concave mirror of radius 24cm, draw the ray diagram of an object at: i) 39cm ii) 15cm iii) 12cm iv) 5cm Rearview mirrors produce images of cars that are a bit smaller than they would be if the mirror were flat. i) Are the mirrors concave or convex? ii) What type and height of image would such a mirror produce of a car that was 1.3m high and 15m behind you, assuming a mirror radius of curvature of 3.2m? A 4.5cm tall object is placed 28cm in front of a spherical mirror. It is desired to produce an image that is upright and 3.5 cm tall. i) what type of mirror should be used? ii) Where is the image located? iii) What is the focal length of the mirror? iv) What is the radius of curvature of the mirror? v) Draw a ray diagram to check this.
More Practice A convex mirror is on the exterior of the passenger side of many trucks. If the focal length of such a mirror is -40cm, what will be the location and height of the image of a car that is 2m tall and 100m behind the mirror? A child looks at a reflective Christmas tree ball ornament that has a diameter of 9cm and sees an image of her face that is half the real size. How far is the child’s face from the ball?