Chapter 18 Mirrors & Lenses

Calculate the angle of total internal reflection in ignoramium (n = 4.0)

Mirrors Smooth surfaces that reflect light waves

Mirrors Mirrors have been used for thousands of years by polishing metal

Mirrors Mirrors producing sharp & well defined images were developed by Jean Foucault in 1857

Mirrors Jean Foucault developed a method to coat glass with silver making excellent mirrors

Object The source of the spreading light waves being observed

Image A reproduction of an object observed through lenses or mirrors

Image When you look into a mirror, you see an image of yourself

Plane Mirror Mirrors on smooth flat surfaces that give regular reflection and good images

Regular Reflection All reflect waves are parallel producing a good image

Diffuse Reflection Reflect waves from a rough surface bounce in all directions producing a poor or no image

Objects & Images Objects & images are represented by arrows as to distinguish the top from the bottom

dodo didi d i = d o h i = h o object image hihi hoho

Virtual Image Light rays focus on a point behind the mirror

Virtual Image Virtual images are erect: image & object pointing in the same direction

Concave Mirrors Light rays are reflect from the inner (caved in) surface part of a hollow sphere

Concave Mirrors Parallel light rays converge when reflected off of a concave mirror

Concave Mirrors Principal axis CF F: focal point C: center of curvature

Focal Point Point at which parallel light rays converge (reflecting from a concave mirror in this case)

Focal Length (f) The distance between the mirror or lens and the focal point

Center of Curvature The center of the sphere whose inner surface makes the concave mirror

Concave Mirrors

d o > C: d i < d o h i < h o

Concave Mirrors

d o = C: d i = d o h i = h o

Concave Mirrors

d o d o h i > h o

Concave Mirrors

d o h o

Problems with Concave Mirrors:

Draw Ray Diagram & Determine Type of Image

Mirror & Lens Formula f d o d i = +

Mirror & Lens Formula f = focal length d o = object distance d i = image distance

Magnification Formula h i d i h o d o =

Magnificaton h i h o M =

Magnification Formula M = magnification h o = object height h i = image height

Problems

A 5.0 cm object is placed 25.0 cm from a concave mirror with a focal length of 10.0 cm. Calculate: d i, h i, & M

A 250 mm object is placed 25 cm from a concave mirror whose center of curvature is 250 mm. Calculate: d i, h i, & M

A 15 cm object placed 75 cm from a concave mirror produces an image 50.0 cm from the mirror. Calculate: f, h i, & M

A 50.0 mm object is placed 0.25 m from a concave mirror with a focal length of 50.0 cm. Calculate: d i, h i, & M

Convex Mirrors Light rays are reflected from the outer surface part of a sphere

Convex Mirrors Parallel light rays diverge when reflected off of a convex mirror

Convex Mirrors d o < f: d i = BM h i < h o

Spherical Aberration The parallel rays reflected off of the edges of a spherical concave mirror miss the focal point, blurring the image.

Spherical Aberration This is corrected by using a parabolic concave mirror

Lenses Transparent material that allows that light to pass through, but refracts the light rays

Concave Lenses Caved in lenses where the center is thinner than the edges

Convex Lenses Bulging lenses where the center is thicker than the edges

Concave Lenses Parallel light rays diverge when passing through a concave lens

Convex Lenses Parallel light rays converge when passing through a convex lens

Convex Lenses

Concave Lenses

Chromatic Aberration The parallel rays passing through a lens are refracted at the edges more so than at the center dispersing the colors

Chromatic Aberration Corrected through lens coating or double lens effect

Achromatic Lens A lens that has been made so that there is no chromatic aberration

Find the image

Eye Glasses Concave lenses correct nearsightedness Convex lenses correct farsightedness

Nearsighted Sees close-up well, but cannot see distances very well

Farsighted Sees distances well, but cannot see close- up very well

A 150 cm object placed 75 cm from a concave mirror produces an image 250 cm from the mirror. Draw & Calculate: f, h i, & M

A 250 cm object placed 1.5 m from a convex lens with a focal length 50.0 cm from the mirror. Calculate: d i, h i, & M

A 350 cm object placed 150 cm from a convex mirror with a focal length -75 cm from the mirror. Calculate: d i, h i, & M

Draw Ray Diagram & Determine Type of Image Mirror

Draw Ray Diagram & Determine Type of Image

Mirror

Draw the Ray Diagram

Convex Lenses