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phy124:lab_7 [2010/03/29 23:34]
mdawber
phy124:lab_7 [2010/04/03 11:58] (current)
mdawber
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+<​html><​STYLE>​ #​jsMath_Warning {display: none} </​STYLE></​html>​
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====== PHY124 Lab 7 - Reflection, Refraction and Images ====== ====== PHY124 Lab 7 - Reflection, Refraction and Images ======

There are two parts to this lab which can be done in either order In Part I you will  study the Laws of Reflection and Refraction, measure the index of refraction of glass and observe dispersion. In Part II you investigate images produced by lenses. There are two parts to this lab which can be done in either order In Part I you will  study the Laws of Reflection and Refraction, measure the index of refraction of glass and observe dispersion. In Part II you investigate images produced by lenses.
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+[[http://​www.ic.sunysb.edu/​Class/​phy122ps/​labs/​dokuwiki/​pdfs/​124lab7worksheet.pdf|Important! You need to print out the 4 page worksheet you find by clicking on this link and bring it with you to your lab session.]]
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+If you need the .pdf version of these instructions you can get them [[http://​www.ic.sunysb.edu/​Class/​phy122ps/​labs/​dokuwiki/​pdfs/​phy124lab7.pdf|here]].
+
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+===== Video =====
+<​flashplayer width=640 height=480>​file=http://​www.ic.sunysb.edu/​Class/​phy122ps/​labs/​phy122vid/​phy124lab7.flv</​flashplayer>​

===== Part I ===== ===== Part I =====
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* Triangular prism   * Triangular prism

-{{124l7fig1.jpg}}+{{124l7fig1.jpg}} ​
+\\ Fig1
==== The laws of reflection and refraction ==== ==== The laws of reflection and refraction ====

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{{124l7fig3.jpg?​600}} {{124l7fig3.jpg?​600}}
+\\ Fig3
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+{{124l7fig4.jpg}} ​
+\\ Fig4

-{{124l7fig4.jpg}}
==== The imaging law for lenses ==== ==== The imaging law for lenses ====

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You will use equation (7.3) and equation (7.4) to measure the focal length and the magnification of a lens with an expected focal length of 5 cm. You will use equation (7.3) and equation (7.4) to measure the focal length and the magnification of a lens with an expected focal length of 5 cm.
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==== Procedure ==== ==== Procedure ====

Make sure that the lam and the painted arrow (the “object”) are placed at one end of the optical bench, with the arrow a few cm in front of the lamp and pointing upward. ​ The arrow and lamp will remain in that position for this part of the experiment. ​ The screen and the lenses will be moved. You will observe two images, one magnified, the other demagnified,​ depending on the position of your lens. Make sure that the lam and the painted arrow (the “object”) are placed at one end of the optical bench, with the arrow a few cm in front of the lamp and pointing upward. ​ The arrow and lamp will remain in that position for this part of the experiment. ​ The screen and the lenses will be moved. You will observe two images, one magnified, the other demagnified,​ depending on the position of your lens.

-Focal length and Magnification for the 5 cm Converging Lens:​Quantitative+=== Focal length and Magnification for the 5 cm Converging Lens:​Quantitative ​===

- Mount the 5 cm (#4) lens in the lens holder. Mount the screen into a holder and place it at +Mount the 5 cm (#4) lens in the lens holder. Mount the screen into a holder and place it at ~ 30 cm from the object. Place the lens between the screen (“image”) and the object as close to the object as possible. Move the lens towards the screen until you can see a sharp image on the screen. ​ First, observe the size and orientation of the object and of the image. ​ Record them into your Execution Sheet. ​ Next, locate the positions of the image, lens and object and record them in your Execution Sheet. Your dominant error in the locations will be the error of the lens position. ​
- ~ 30 cm from the object. Place the lens between the screen (“image”) and the object as close to the object as possible. Move the lens towards the screen until you can see a sharp image on the screen. ​ First, observe the size and orientation of the object and of the image. ​ Record them into your Execution Sheet. ​ Next, locate the positions of the image, lens and object and record them in your Execution Sheet. Your dominant error in the locations will be the error of the lens position. ​+

Note that the lens is not centered on the lens holder but offset by 0.6 cm. Make sure you note the orientation of the lens. If it is oriented as shown in Fig. 4, so that the lens is closer to the screen, you must increase the lens position by 0.6 cm. If the lens is further from the screen you must decrease the lens position by 0.6 cm.  Assume an error in the lens position of 0.2 cm. Estimate the errors of the image and object size (\$h_{i}\$ and \$h_{o}\$) as well.  Note that the lens is not centered on the lens holder but offset by 0.6 cm. Make sure you note the orientation of the lens. If it is oriented as shown in Fig. 4, so that the lens is closer to the screen, you must increase the lens position by 0.6 cm. If the lens is further from the screen you must decrease the lens position by 0.6 cm.  Assume an error in the lens position of 0.2 cm. Estimate the errors of the image and object size (\$h_{i}\$ and \$h_{o}\$) as well.
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Compare your obtained value of f with the nominal value of 5 cm, is it consistent? Compare your obtained value of f with the nominal value of 5 cm, is it consistent?

-Find the magnification from the measured heights of the image and object using \$m=h_{o}/h_{i}\$.+Find the magnification from the measured heights of the image and object using \$m=h_{i}/h_{o}\$.

-Calculate the error in the measured magnification from the errors in hi and ho using equation (E.7) in Error and Uncertainty.  ​+Calculate the error in the measured magnification from the errors in \$h_{i}\$ ​and \$h_{o}\$ ​using equation (E.7) in Error and Uncertainty.  ​

Calculate the magnification from the measured image and object distances using equation (7.4).  ​ Calculate the magnification from the measured image and object distances using equation (7.4).  ​
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Move the lens to another position, closer to the screen, where you get a sharp image of a different size. Record the same data for that position. No errors are needed here. Move the lens to another position, closer to the screen, where you get a sharp image of a different size. Record the same data for that position. No errors are needed here.

-On the graph paper on Execution Sheet 3 make a drawing – to scale as before – containing object and image arrows and the lens with object and image distance and the nominal focal length of 5 cm. Reconstruct in your drawing the image with the two principal rays (see Ch22 sheet 20). Get the measured magnification \$m=h_{o}/h_{i}\$  and compare it to the value obtained for your 1st lens position. ​ +On the graph paper on your worksheet ​make a drawing – to scale as before – containing object and image arrows and the lens with object and image distance and the nominal focal length of 5 cm. Reconstruct in your drawing the image with the two principal rays (see Ch22 sheet 20). Get the measured magnification \$m=h_{i}/h_{o}\$  and compare it to the value obtained for your 1st lens position. ​
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+=== Image and Magnification for the 10 cm Diverging Lens: Qualitative only ===

+Mount the 10 cm (#3) diverging lens in the lens holder. Place the lens at as close as possible to the object. Try to make an image on the screen by moving the lens and screen around (verify that you don’t in fact produce an image on the screen). Remove the screen and place your eye close to the lens so that you can observe the image the lens produces from the object. Describe on your worksheet whether the image (what you see) appears upright/​inverted,​ magnified/​demagnified with respect to the original object

+Slide the lens away from the object and, keeping your eye close to the lens, state on your worksheet whether the properties of the image, apart from the size, change as you increase the distance of the lens from the object., i.e. is the image for any object distance upright/​inverted,​ magnified/​demagnified. Is the image real or virtual? ​
phy124/lab_7.txt · Last modified: 2010/04/03 11:58 by mdawber