Please pick up a lens.

Transcription

1 Lene & Image A len or mirror can bend ray of light to make an image. There are two different kind of lene: Converging and diverging. Mirror follow the ame rule. There are two different kind of image: Real and virtual. Optical device that you look through ue virtual image; thoe that project image ue real image. Pleae pick up a len. Warming Up n inθ = n 2 inθ 2 Mirror Image Thi i a virtual image.

2 Converging & Diverging Lene f i + f i - Characterizing Lene. What i the power of a converging len with focal length 20 cm? 2. What i the power of a diverging len of focal length -20 cm? Adding Lene For two lene in cloe proximity: P total = P + P 2 A converging len ha a focal length of 0 cm i placed next to a econd len with a focal length 20 cm. What i the focal length of the combination of the two lene?

3 Real Image Object height h Ray leave P (and Q and R) in every direction. For clarity, only a few are hown. Q P R Object Optical axi Object plane Special ray Near focal point Len plane f All the ray leaving one point in the object plane (P) that reach the len are refracted by it and converge to one point in the image plane (P ). f Far focal point Image plane P Thi i a real image. R Q Image height h + ' = f h = ' Sign: : + f: + : + Doing the Number A 2.0-cm-tall object i 40 cm in front of a converging len with a 20 cm focal length. Calculate the image poition and height. + ' = f h = ' Real image on the retina. h h Fixed About.7 cm=0.07 m

4 Retina Diplay My laptop i aid to have a retina diplay. My laptop diplay ha 00 pixel / cm, o each pixel i m wide. I read with my creen 48 cm (0.48 m) away from my eye. Aume that my retina i 0.07 m from the len in my eye. What i the ize, on my retina, of the image of a ingle pixel? + ' = f h = ' 76. A lide projector need to create a 98-cm-high image of a 2.0-cm-tall lide. The creen i 300 cm from the lide. a. What focal length doe the len need? Aume that it i a thin len. b. How far hould you place the len from the lide? + ' = f + ' = 2.0 m Virtual Image P Diverging ray from P P Virtual image Object f + ' = f h = ' Your eye ee the virtual image at P. Sign: : + f: + : -

5 Doing the Number A 2.0-cm-tall object i 20 cm in front of a converging len with a 40 cm focal length. When I look through the len at the object, where doe it appear to be? How tall i it? + ' = f h = ' Real Image + ' = f h = ' Sign: : + f: + : + Warming Up The overhead projector i 2.0 m from the creen. I place a lide on the deck over the overhead to project it. I need to make the image larger, o I mut move the overhead back from the creen. Thi make the image out of focu. How do I need to move the len in order to retore focu?! Lower it toward + ' = f the lide Raie it away from the lide

6 Warming Up To ue a lide projector to project a 98-cm-high image of a 2.0-cm-tall lide with the creen 300 cm from the lide: a. What focal length len i needed? b. How from from the lide hould be len be placed? + ' = f h = ' Doing the Number A tudent look at a 2.0 cm high object through a diverging len of focal length -0 cm. The object i 20 cm from the len. Where doe the image appear to be? How large i it? + ' = f h = ' The Converging Mirror

7 Doing the Number A 2.0-cm-tall object i 40 cm in front of a converging mirror with a 20 cm focal length. Calculate the image poition and height. + ' = f h = ' The Diverging Mirror Object in Mirror... A dinoaur i 0 m from a jeep, which ha a diverging mirror with a power of -.5 D. Where doe the image of the dinoaur appear to be?

8 The Simplet Camera The Camera The Telephoto Len Why doe the telephoto len project o far in front of the camera?

9 The Firetarter A len can be ued to tart a fire by focuing an image of the un onto a piece of flammable material. All other thing being equal, would a len with a hort focal length or a long focal length be better a a fire tarter? Explain. Snaphot The image of a.5 m tall woman i 5 mm high on the 35 mm film in a camera. In the camera, the len i 50 mm from the film. How far i the woman from the camera? + ' = f h = ' The Eye

10 The Image on the Retina f = + ' f = 60 + Varie Fixed About.7 cm=0.07 m / i about 60 A varie, change power, /f. The Number Ditance Neceary Power Infinity 60.0 m m m 64 f = + ' f = 60 + Only approximate. Not really true. Figuring the Near Point People in their early 20 have about 0 diopter of accommodation. For thi range of accommodation, what i the near point? f = 60 +

11 Adding Lene For two lene in cloe proximity: P total = P + P 2 A converging len with a focal length of 0 cm i placed next to a econd len with a focal length 20 cm. What i the focal length of the combination of the two lene? Uing a Magnifier A peron with a near point of 0 cm ue a magnifying gla with focal length 5.0 cm. What i hi new near point? f = 60 + P total = P + P 2 Warming Up A camera i focued on an object at a ditance of.0 m. Now, the object i moved cloer, to a ditance of 0.50 m. How mut the poition of the len be changed to keep the image in focu? + ' = f

12 The Differently Viioned: Prebyopia 5 Accommodation in diopter Age in year The Differently Viioned: Prebyopia A woman who ha never needed viion correction find that, a he age, her near point grow to.0 m too ditant for comfortable reading. Her ditant viion i till quite good. If he would like to read at the more reaonable ditance of 25 cm, what power len doe he need in a pair of reading glae? With thi len in place, what i her new far point? What he ha: near point: 6, far point: 60 What he want: near point: 64 What he need: converging len: +3 What he get: far point: 63, far point = 0.33 m The Differently Viioned: Myopia A man ha a near point of 0 cm and a far point of 20 cm. What power len will correct hi viion? Len i too trong. Need a diverging len. What he ha: near point: 70, far point: 65 What he want: far point: 60 What he need: diverging len: -5 What he get: near point: 65, o 0.20 m

13 The Differently Viioned: Hyperopia A farighted woman ha a near point of 0.50 m. She buy a et of cheap reading glae labeled What i her near point when wearing thee glae? In the water, an octopu ha very good viion. In the air, would it be nearighted or farighted? The Truth about Piggy Piggy i myopic. The optical ytem of hi eye i too trong. What ort of corrective len doe he need? From Lord of the Flie:! In the hort chill of dawn the four boy gathered round the black mudge where the fire had been, while Ralph knelt and blew. Grey, feathery ahe curried hither and thither at hi breath, but no park hone among them. The twin watched anxiouly and Piggy at expreionle behind the luminou wall of hi myopia...! Ralph brought hi face to within a couple of feet of Piggy.! Can you ee me?! A bit.