Mirrors And Lenses

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# Mirrors And Lenses - PowerPoint PPT Presentation

Mirrors And Lenses. Chapter 23. Introduction. Images can be formed by plane or spherical mirrors and by lenses. Ray diagrams will be used. Plane and Curved Mirrors. Important terms: Object distance (p) Image Formed where light rays actually intersect or where they appear to originate

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## PowerPoint Slideshow about 'Mirrors And Lenses' - rene

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Presentation Transcript
Introduction
• Images can be formed by plane or spherical mirrors and by lenses.
• Ray diagrams will be used
Plane and Curved Mirrors
• Important terms:
• Object distance (p)
• Image
• Formed where light rays actually intersect or where they appear to originate
• Image distance (q)
Two Types of Images
• Real image
• Light rays actually intersect and pass through the image point.
• May be formed on a screen
Virtual Image
• Light rays only appear to come from the image point.
• Cannot be formed on a screen
• Example: images in flat mirrors
Flat Mirrors
• The image distance(q)always equals the object distance(p).

23.1, 29.1

Flat Mirrors Summary
• The image distance always equals the object distance.
• The image height (h’) always equals the object height (h).
• Images are left-right reversed.
• Images are always virtual.
• Images are always upright.
• Lateral magnification (M) is always 1.
Applications of Flat Mirrors
• Rearview mirrors in cars
• Dressing room mirrors
• Bathroom mirrors

242, 29.2

Concave Mirrors
• Concave mirrors are a part of a sphere.

236, 380

Images formed may be real or virtual.
• The type of image depends upon the object location.
Concave Mirrors Summary
• Are a part of a sphere
• Light reflects from the inner surface.
• Images formed may be real or virtual.
• Depends upon object location
• Images may be upright or inverted.
• Sometimes called converging mirrors
• Focal length is positive.
Important Terms
• Principal axis
• Image point
• Image distance (q)
• Object distance (p)
• Center of curvature C
• Focal point (F)
• Focal length (f)

23.9

Spherical Aberration
• Spherical aberration is an undesirable characteristic that is present in all spherical mirrors
• It may be eliminated by using parabolic mirrors.
Parabolic Mirror Applications
• Satellite dishes
• Flashlights
• Projector bulbs
• Astronomical telescopes
Ray Diagrams
• Front side and back side of the mirror
• Light rays are always in front of the mirror.
• This is taken to be the left side.
Three Important Rays
• The intersection of any two rays will locate the image.
• Parallel rays that come from infinity always pass through the focal point
• When the object is at infinity, the image is at the focal point

382, 188, 382, 383

Equations for Concave Mirrors
• Magnification equation:
• The mirror equation
Applications of Concave Mirrors
• Shaving mirrors
• Makeup mirrors
• Solar cookers
Convex Mirrors
• Convex mirrors are a part of a sphere.

380

Images formed are always virtual.
• They always lie behind the mirror.
Convex Mirrors Summary
• Are a part of a sphere
• Light reflects from the outer surface
• Images formed are always virtual
• They always lie behind the mirror.
• Images are always upright
• Sometimes called diverging mirrors
• Focal length is negative
Ray Diagrams for Convex Mirrors
• Front side and back side of the mirror
• Light rays are always in front of the mirror.
Ray Diagrams
• See Figure 23.11
• Three important rays (see pg. 765)

23.11, 240, 384, 23.12

• When the object is at infinity, the image is at the focal point.
Equations for Convex Mirrors
• These equations are the same as before.
• Magnification equation
• The mirror equation
Sign Conventions for Mirrors
• SeeTable 23.1on page 765
Applications of Convex Mirrors
• Side view mirrors on cars
• Shoplifting mirrors
Questions

1 - 4, 7

Pg. 783

Images Formed By Refraction
• Sign conventions
• See Table 23.2 on page 770
Apparent Depth
• Flat refracting surfaces
• Apparent Depth(q)vs. Actual Depth(p)
• n1 is below the surface

23.16, 243

Atmospheric Refraction
• The Sun is not where it appears to be.
• It can be seen even though it is below the horizon.
• Sun dogs and Moon dogs
• Halos on cold winter days or nights
• Refraction through hexagonal ice crystals
• Mirages

23.21

Thin Lenses
• A thin lens is a piece of glass or plastic which is ground so that its surfaces are segments of either spheres or planes.
• A thin lens acts like two prisms.
Refraction in Optical Instruments
• Thin lenses are used to form images by refraction in optical instruments
• Cameras
• Projectors
• Microscopes
• Telescopes
• Binoculars
• Magnifying glasses

248, 249

The Thin Lens Equation
• The lens equation is virtually identical to the mirror equation.

23.23

Common Lens Shapes
• Converging lenses
• Biconvex
• Convex-concave
• Plano-convex
• Diverging lenses
• Biconcave
• Convex-concave
• Plano-concave

64, 66, 67

Convex Lenses
• Convex lenses form virtual images when the object is within the focal length of the lens.
• Example: a simple magnifying glass.
• Convex lenses form real images when the object is beyond the focal length of the lens.

250

Concave Lenses
• Concave lenses never form real images.251
Thin Lens Concepts
• Focal point(F)
• Thin lenses have two.
• Parallel light rays pass through the lens and converge or appear to originate here.
• Focal length(f)

68

Magnification Equation
• Equation for magnification:
Thin Lens Equation
• Thin-lens equation:
Lens Maker’s Equation
• R1 is for the surface closest to the object
The front of the lens
• The side from which light approaches
Sign Conventions
• Sign conventions (Table 23.3) pg. 775
• Extremely important!
Ray Diagrams
• Ray diagrams (similar to mirrors)
• Three important rays
• Rays that come from infinity always pass through the focal point.
• When the object is at infinity, the image is at or appears to be at the focal point.
• The intersection of two rays will locate the image.

247, 23.25, 69, 70

Thin Lens Combinations
• The image formed by the first lens serves as the“object”for the second lens.

256

Spherical Aberration
• Similar to that produced by mirrors
• In mirrors, it can be reduced by using parabolic surfaces.
• Parabolic mirrors are used in headlights, satellite dishes, searchlights, and astronomical mirrors.
• Parabolic surfaces are more expensive to make.

23.30

Chromatic Aberration
• Chromatic aberration results because different wavelengths have different indices of refraction.
• Chromatic aberration is produced by lenses but not by mirrors.
Chromatic Aberration may be reduced by using combinations of converging and diverging lenses made from different types of glass
• This is expensive.
Questions

9 - 13

Pg. 784