Chapter 18 Mirrors and Lenses

18.2 Lenses A. Types of Lenses A. Types of Lenses B. Convex Lenses B. Convex Lenses C. Concave Lenses C. Concave Lenses D. Optical Instruments that Use Lenses D. Optical Instruments that Use Lenses

A. Types of Lenses 1. A lens is made of transparent material with a refractive index larger than air. 1. A lens is made of transparent material with a refractive index larger than air. 2. Each face of the lens is part of a sphere and can be convex, concave, or flat. 2. Each face of the lens is part of a sphere and can be convex, concave, or flat. 3. A convex lens is thicker in the middle than at the edges and are converging lenses. 3. A convex lens is thicker in the middle than at the edges and are converging lenses. 4. A concave lens is thinner in the middle and is a diverging lens. 4. A concave lens is thinner in the middle and is a diverging lens.

B. Convex Lenses 1. The thin lens model. 1. The thin lens model. 2. Real Images from Convex Lenses. 2. Real Images from Convex Lenses. 3. Lens/Mirror Equation conventions 3. Lens/Mirror Equation conventions a. f is positive for convex lenses a. f is positive for convex lenses b. f is negative for concave lenses b. f is negative for concave lenses c. d o is positive on the object side of the lens c. d o is positive on the object side of the lens d. d i is positive on the other side of the lens d. d i is positive on the other side of the lens e. d i is negative on the object side of the lens where images are virtual. e. d i is negative on the object side of the lens where images are virtual.

4. Why use a larger lens? 4. Why use a larger lens? More light gathering ability More light gathering ability Virtual images Virtual images Images formed when the object is inside the focal point. Images formed when the object is inside the focal point.

C. Concave Lenses Images formed by concave lenses are virtual, erect, and reduced in size no matter how far from the lens the object is placed. Images formed by concave lenses are virtual, erect, and reduced in size no matter how far from the lens the object is placed. Defects in lenses. Defects in lenses. Spherical aberration Spherical aberration Chromatic aberration Chromatic aberration Achromatic lens Achromatic lens

D. Optical Instruments that use Lenses Nearsighted or myopic eyes Nearsighted or myopic eyes Farsighted or hyperopia eyes Farsighted or hyperopia eyes Astigmatism Astigmatism Contact Lenses Contact Lenses Microscopes Microscopes Telescopes Telescopes