Lecture 26: July 29 th 2009

1. Lecture 26: July 29th 2009 Physics for Scientists and Engineers II Physics for Scientists and Engineers II , Summer Semester 2009

2. Ray Diagrams for Thin Lenses Physics for Scientists and Engineers II , Summer Semester 2009

3. Combination of Thin Lenses Similar to the procedure we used when calculating the effect of two refracting surfaces: Step 1: Ignore lens 2 and calculate the image position due to lens 1. Step 2: Determine whether image position from Step 1 is in front or behind lens 2.  In front of lens 2: Object position for lens 2 positive (real object)  Behind lens 2: Object position for lens 2 is negative (virtual object) ….and determine the distance to lens 2, of course. Step 3: Determine the image position (of the object determined in step 2) due to lens 2. Overall magnification: Physics for Scientists and Engineers II , Summer Semester 2009

4. Example of Combination of Thin Lenses Physics for Scientists and Engineers II , Summer Semester 2009

5. Example – Step 1 (ignore lens 2) Physics for Scientists and Engineers II , Summer Semester 2009

6. Example – Step 2 (ignore lens 2) Physics for Scientists and Engineers II , Summer Semester 2009

7. Example – Step 3 (ignore lens 1) Physics for Scientists and Engineers II , Summer Semester 2009

8. Example of Combination of Thin Lenses Physics for Scientists and Engineers II , Summer Semester 2009

9. The Simple Magnifier – Angle Subtended Objects appear larger if the angle q subtended at the eye is larger. Eye Get closer to the object and q becomes larger  object appears larger. Problem: At some point the human eye can no longer focus on the object. Typically, the closest distance is 25cm, the “near point of the eye” (varies individually, especially with age). Eye Physics for Scientists and Engineers II , Summer Semester 2009

10. The Simple Magnifier Adding a lens and putting eye close to the lens such that the image appears at 25cm (able to focus on the image). Eye Physics for Scientists and Engineers II , Summer Semester 2009

11. Angular Magnification: The Simple Magnifier Physics for Scientists and Engineers II , Summer Semester 2009

12. The Compound Microscope – Two converging lenses Physics for Scientists and Engineers II , Summer Semester 2009

13. The Compound Microscope – Magnification Magnification Using Compound Microscope: Physics for Scientists and Engineers II , Summer Semester 2009

14. The Refracting Telescope Physics for Scientists and Engineers II , Summer Semester 2009

15. Chapter 37: Condition for Interference of Light Waves Interference = Superposition (adding) of waves S1 S2 S1 S2 Example of Constructive Interference Physics for Scientists and Engineers II , Summer Semester 2009

16. Condition for Interference of Light Waves S1 S2 S1 S2 Example of Destructive Interference • Conditions for Interference: • Light from two sources must be “coherent”. That means, the relative phase between S1 and S2 must remain constant. • The light should be monochromatic (single wavelength). Physics for Scientists and Engineers II , Summer Semester 2009

17. Young’s Double-Slit Experiment Diffraction of light occurs. Barrier with two small openings. Monochromatic light. Physics for Scientists and Engineers II , Summer Semester 2009

18. Young’s Double-Slit Experiment Maximum Minimum Maximum Minimum Maximum Screen Constructive and destructive interference depending on direction. Physics for Scientists and Engineers II , Summer Semester 2009

19. Center: Bright Spot Constructive interference (bright fringe on screen) Screen Physics for Scientists and Engineers II , Summer Semester 2009

20. First Minimum (Destructive Interference) Destructive interference (Dark fringe on screen) Screen Physics for Scientists and Engineers II , Summer Semester 2009

21. The next Maximum Constructive interference (Bright fringe on screen) Screen Physics for Scientists and Engineers II , Summer Semester 2009

22. P Light Waves in Interference y S1 Q d O S2 Physics for Scientists and Engineers II , Summer Semester 2009