Chapter 34. Images. Two Types of Images. A Common Mirage. Plane Mirrors, Extended Object. Plane Mirrors, Point Object

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1 Capter Images One o te most important uses o te basic laws governing ligt is te production o images. Images are critical to a variety o ields and industries ranging rom entertainment, security, and medicine A clear seet o polaroid is placed on top o a similar seet so tat teir polarizing axes make an angle o 0 wit eac oter. Te ratio o te intensity o emerging ligt to incident unpolarized ligt is: A. / B. / C. / D. / E. /8 In tis capter we deine and classiy images, and ten classiy several basic ways in wic t can be produced. - ject Two Types o Images lens real image A Common Mirage Ligt travels aster troug warm air warmer air as smaller index o reraction tan colder air reraction o ligt near ot suraces For server in car, ligt appears to be coming rom te road top aead, but is really coming rom sky. ject mirror virtual image Image: a reproduction derived rom ligt Real Image: ligt rays actually pass troug image, really exists in space (or on a screen or example) weter you are looking or not Fig. - Plane Mirrors, Point Object Plane mirror is a lat relecting surace. Plane Mirrors, Extended Object Eac point source o ligt in te extended ject is mapped to a point in te image Fig. - Fig. - Plane Mirror: i = p Since I is a virtual image i < 0 Identical triangles Ib = Ob Fig. - Fig. -5 Virtual Image: no ligt rays actually pass troug image. Only appear to be coming rom image. Image only exists wen rays are traced back to perceived - location o source

2 Fig Plane Mirrors, Mirror Maze Your e traces incoming rays straigt back, and cannot know tat te rays may ave actually been relected many times plane concave convex Fig. -7 Sperical Mirrors, Making a Sperical Mirror Plane mirror Concave Mirror. Center o Curvature C: in ront at ininity in ront but closer. Field o view wide smaller. Image i=p i >p. Image eigt image eigt = ject eigt image eigt > ject eigt - 7 Plane mirror Convex Mirror. Center o Curvature C: in ront at ininity beind mirror and closer. Field o view wide larger. Image i=p i <p. Image eigt image eigt = ject eigt image eigt < ject eigt - 8 Sperical Mirrors, Focal Points o Sperical Mirrors concave convex Images rom Sperical Mirrors Start wit rays leaving a point on ject, were t intersect, or appear to intersect marks te corresponding point on te image. Fig. -9 Fig. -8 Sperical Mirror: = r Real images orm on te side were te ject is located (side to wic ligt is going). Virtual images orm on te opposite side. ' Sperical Mirror: + = Lateral Magniication: m = p i i p Locating Images by Drawing Rays Proo o te magniication equation Similar triangles (are angles same) Fig. -0 Fig. -0 de cd de = cd = i, ca = p, = m ab ca ab i m = (magniication) p r > 0 or concave (real ocal point) r < 0 or convex (virtual ocal point) Lateral Magniication: m = A ray parallel to central axis relects troug F. A ray tat relects rom mirror ater passing troug F, emerges parallel to central axis. A ray tat relects rom mirror ater passing troug C, returns along itsel. A ray tat relects rom mirror ater passing troug c is relected symmetrically about te central axis - -

3 Sperical Reracting Suraces Tin Lenses Converging lens Fig. - Diverging lens Real images orm on te side o a reracting surace tat is opposite te ject (side to wic ligt is going). Virtual images orm on te same side as te ject. n n n n Sperical Reracting Surace: + = Tin Lens: p i Fig. - = r r = + Tin Lens in air: ( n ) Lens only can unction i te index o te lens is dierent tan tat o its surrounding medium - Images rom Tin Lenses Locating Images o Extended Objects by Drawing Rays Fig. - Real images orm on te side o a lens tat is opposite te ject (side to wic ligt is going). Virtual images orm on te same side as te ject. Fig. -5 Two Lens System A ootball ield is about 00 meters long. Te time or ligt to travel tis distance is about: O p i p I Lens O Lens i I A. 0.x0-6 s B. 0. ms C. min D. r E. yr. Let p be te distance o ject O rom Lens. Use equation and/or principle rays to determine te distance to te image o Lens, i.. Ignore Lens, and use I as te ject O. I O is located bond Lens, ten use a negative ject distance p. Determine i using te equation and/or principle rays to locate te inal image I. Te net magniication is: M = m m Wen ject aces a convex reracting surace r is positive. Wen it aces a concave surace, r is negative. CAUTION: Reverse o o mirror sign convention! A ray initially parallel to central axis will pass troug F. A ray tat initially passes troug F, will emerge parallel to central axis. A ray tat initially is directed toward te center o te lens will emerge rom te lens wit no cange in its direction (te two sides o te lens at te center are almost parallel)

4 Optical Instruments, Simple Magniying Lens Optical Instruments, Compound Microscope O close to F I close to F Can make an ject appear larger (greater angular magniication) by simply bringing it closer to your e. However, te e cannot ocus on jects closer tat te near point p n ~5 cm BIG & BLURRY IMAGE A simple magniying lens allows te ject to be placed close by making a large virtual image tat is ar away. 5 cm Simple Magniier: m Fig. -7 Object at F ' m = = and ' 5 cm -9 Mag. Lens Fig. -8 i s m = = since i s and p p s 5 cm M = mm = magniication compounded (microscope) -0 Fig. -9 Optical Instruments, Reracting Telescope m I close to F and F =, =, m = Mag. Lens ' (telescope) ' Tree Proos, Te Sperical Mirror Formula β = α + and γ = α + = β α = ( γ α ) α + γ = β ac ac ac ac α =, β = = co p cc r ac ac γ = = Fig. -0 CI i = r r = ac ac ac + = + = p i p i Tree Proos, Te Reracting Surace Formula n sin = n sin n n i and are small = α + β and β = + γ n ( α + β ) = n ( β γ ) nα + n γ = ( n n ) β ac ac ac α ; β = ; γ p r i Fig. - ac ac ac n ( ) + n = n n p i r n n n n + = Tree Proos, Te Tin Lens Formulas Fig. - n n n n + = were n = and n = n n n + = ( Eq. -) p ' i ' r ' p '' = i ' + L n n n n + = ; i L small + = ( Eq. -5 ) i ' + L i '' r '' i ' i '' r '' ( Eq. - ) + ( Eq. -5) + = ( n ) + = ( n ) p ' i '' r ' r ' p i r ' r '' -

5 Te time or a radar signal to travel to te Moon and back, a one-way distance o about m, is: A.. s B..5 s C. 8 s D. 8min E. 0 6 s Radio waves o wavelengt cm ave a requency o: Ligt o uniorm intensity sines perpendicularly on a totally absorbing surace, ully illuminating te surace. I te area o te surace is decreased: A. te radiation pressure increases and te radiation orce increases B. te radiation pressure increases and te radiation orce decreases C. te radiation pressure stays te same and te radiation orce increases D. te radiation pressure stays te same and te radiation orce decreases E. te radiation pressure decreases and te radiation orce decreases A. MHz B. 9MHz C. 00MHz D. 0, 000MHz E. 900MHz Te ligt intensity 0m rom a point source is 000W/m. Te intensity 00m rom te same source is: A. 000W/m B. 00W/m C. 0W/m D. W/m E. 0.W/m 5 6 5