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Optics: Mirrors and Lenses 2. Convex Mirrors. Rays diverge so the image is virtual f is half of the radius of curvature (negative) Image is virtual, erect and reduced Wide area reflected so used in stores, rear view mirrors, side view mirrors (objects in mirror…). Lenses.
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Convex Mirrors • Rays diverge so the image is virtual • f is half of the radius of curvature (negative) • Image is virtual, erect and reduced • Wide area reflected so used in stores, rear view mirrors, side view mirrors (objects in mirror…)
Lenses • Glass or Plastic or Polycarbonate with n greater than 1 • 2 sides (faces) of the lens • Each side can be flat OR part of a sphere
Convex and Concave Lenses • Convex • thicker at the center than the edges • Converging • Refract light rays so they meet
Convex and Concave Lenses • Concave • Thinner at the center than the edges • Diverging
Covex Lens: Real Image • 3 ray diagram – from top of object • First ray parallel to axis, then through focal point • Second ray through F’ then parallel to axis • Third ray is through center of lens • Lens assumed very thin • f depends on • Shape of lens • n of lens material
Covex Lens: Real Image • Beyond 2F – image real, inverted, and reduced • Approaching F – image real, inverted enlarged • At 2F image is at 2F – inverted, same size
Covex Lens: Virtual Image • If the object is at F, ray emerge in a parallel beam • If the object between F and lens then the rays DO NOT converge on opposite side of lens • image is virtual, erect and enlarged
Concave Lens: Virtual Image • All rays diverge • Virtual image is erect and reduced • Doesn’t matter how far object is from the lens • f is negative, corrects near sightedness