Physics 2102 Jonathan Dowling QuickTime and a decompressor are needed to see this picture Lecture 36 FRI 17 APR 34 1 4 Geometrical optics QuickTime and a decompressor are needed to see this picture QuickTime and a decompressor are needed to see this picture QuickTime and a decompressor are needed to see this picture Geometrical Optics Geometrical optics rough approximation light rays particles that travel in straight lines Physical Classical optics good approximation electromagnetic waves which have amplitude and phase that can change Quantum Optics exact Light is BOTH a particle photon and a wave wave particle duality Plane Mirrors Light rays reflect on a plane mirror and produce a virtual image behind the mirror What s a virtual image It means the light rays are NOT coming from a real point there is no light where the image appears object image i p for a plane mirror Ray Tracing Plane Flat Mirror QuickTime and a decompressor are needed to see this picture Draw Two Rays From Object to Point on Mirror aw Perpendicular Line to Mirror From Each Point Use i r To Draw Reflected Rays to Eye tend Reflected Rays Behind Mirror to Find Virtual I Ray Tracing Plane Flat Mirror m ho hi 1 QuickTime and a decompressor are needed to see this picture hi ho ho do Image distance is minus Object distance do di means image is behind minus the mirror and do di means image is behind mirror same distance object is in front Virtual image means no light actually is at the image location optical illusion Magnification m 1 means image has same Spherical mirrors point is at half the curvatuire radius f r 2 arallel to the axis reflect through the focal point hitting the mirror after going to the focal point emerge par going through the center of curvature reflect back on themse Concave mirrors r 0 Convex mirrors r 0 Images from spherical mirrors Consider an object placed between the focal point and the mirror It will produce a virtual image behind the mirror When the object is at the focal point the image is produced at infinity If the object is beyond the focal point a real image forms at a distance i from the mirror lateral magnification 1 1 1 p i f i m p Check the signs ay Tracing Concave Mirror Image Outside Focal Poin orizontal Ray Bounces Through Focal Point y Through Focal Point Bounces into Horizontal QuickTime and a decompressor are needed to see this picture ay Through Center Bounces Straight Back At cha Rays Cross at Image Point Image is Real Light At Image Inverted and Shrunk m ho hi is minus and m 1 and do and di are both ay Tracing Concave Mirror Image Inside Focal Point orizontal Ray Bounces Through Focal Point y Through Focal Point Bounces into Horizontal QuickTime and a decompressor are needed to see this picture ay Through Center Bounces Straight Back At cha oject Behind Mirror to Cross at Virtual Image s Virtual no light Upright and Enlarged m h o hi is plus and di are on opposite sides of mirror Ray Tracing Convex Mirror rizontal Ray Bounces Into Line of Focal Point y Towards Focal Point Bounces into Horizontal QuickTime and a decompressor are needed to see this picture ay Towards Center Bounces Straight Back At cha oject Rays Behind Mirror Cross at Virtual Image is Virtual no light Upright and Shrunk m h o hi is plus an and di are on opposite sides of mirror Example An object 2cm high is located 10cm from a convex mirror with a radius of curvature of 10cm Locate the image and find its height ocal length f r 2 10cm 2 5cm osition 1 i 1 f 1 p 1 5cm 1 10cm 3 10cm i 10 3cm 3 33 cm the image is virtu ication m i p 3 33cm 10cm 0 33 upright smaller e object image is 2cm the image height is 0 33 x 2cm 0 67 c Newton s Reflecting Telescope QuickTime and a decompressor are needed to see this picture Hubble Hubble Toil and Trouble A star seen with a ground telescope and with old Hubble The same star seen with the new Hubble Hubble mirror screw up The central region of the mirror was flatter than it should be by just one fiftieth of the width of a human hair This is equivalent to only four wavelengths of visible light but it was enough One insider said that the Hubble mirror was very accurate very accurately the wrong shape Before and after QuickTime and a decompressor are needed to see this picture QuickTime and a decompressor are needed to see this picture QuickTime and a decompressor are needed to see this picture QuickTime and a decompressor are needed to see this picture
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