Lenses & critical angle pptx

Lenses & critical angle pptx

1. Choose a word that describes the three pictures ( https://www.menti.com/rpzwiq26db )

2. LEARNING OBJECTIVES Define critical angle and total internal reflection Observe the occurrence of the total internal reflection for different prisms. 1. Critical angle and total internal reflection Key concept : Relationships, Related concepts : Movement, energy, Global Context : Personal and cultural expressions

3. Use this link https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html and follow the steps below: Select “more tools” Select “ray” Select “glass” as the material for the upper medium. Select “air” as the material for the lower medium. Click on the “angle” icon Start increasing the angle of incidence slowly from 10 o to 80 o On your notebook describe what happens. Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development Critical Angle: Textbook pages 251-253

4. Use this link https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html and follow the steps below: Select “more tools” Select “ray” Select “air” as the material for the upper medium. Select “glass” as the material for the lower medium. Click on the “angle” icon Start increasing the angle of incidence slowly from 10 o to 80 o On your notebook describe what happens. Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development Critical Angle: Textbook pages 251-253

5. Use this link https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html and follow the steps below: Select “more tools” Select “ray” Select “water” as the material for the upper medium. Select “glass” as the material for the lower medium. Click on the “angle” icon Start increasing the angle of incidence slowly from 10 o to 80 o On your notebook describe what happens. Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development Critical Angle: Textbook pages 251-253

6. Based on your observations: Define critical angle. State two conditions for critical angle to be observed What happens when you exceed the critical angle Key concept : Relationships, Related concepts : Movement, energy, Global Context : Personal and cultural expressions Critical Angle You can watch this video to help you answering the questions https://youtu.be/NAaHPRsveJk

7. After watching the video, define critical angle. Critical angle: is the angle of incidence at which the angle of refraction is 90 o . Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

8. Total internal reflection: Explain when total internal reflection occur. When the angle of incidence  the critical angle of a medium, When light travels from more dense to less dense mediums Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

9. LEARNING OBJECTIVES Solve mathematical problems related to critical angle Describe some of the applications of the total internal reflection. 2. Critical angle and total internal reflection Key concept : Relationships, Related concepts : Movement, energy, Global Context : Personal and cultural expressions

10. Mirage appears in a hot day due to the: ( Padlet ) High humidity in the atmosphere Reflection of sun light on the surface of earth The vaporization of water The refraction and reflection of light https://youtu.be/_M0FcpQWh5E

11. https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html The diagram shows total internal reflection in a prism ; the light is turned through 90 o The diagram shows total internal reflection in a prism ; the light is turned through 180 o . Total internal reflection Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

12. Total internal reflection Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development https://youtu.be/NFaAAtQoDmE

13. Total internal reflection Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

14. Fiber optics: Endoscopes to Telephones ; Periscopes; Single lens reflex (SLR) camera; Binoculars. Applications to total internal reflection Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

15. Read pages 253 & 254 from your textbook. Answer questions 1-3 page 255 on your notebook Applications to total internal reflection Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

16. n i sin i = n r sin r n i sin i = n r sin 90 Critical angle n i sin θ c = n r sin θ c = n r / n i Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

17.   Question 1: Calculate the critical angle for a water-air interface. ( n water = 1.33) Question 2: Calculate the refractive index of a medium whose critical angle is 42˚ at the medium-air interface. Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

18. https://youtu.be/geDnCu78dvE Mirage appears in a hot day due to the: High humidity in the atmosphere Reflection of sun light on the surface of earth The vaporization of water The refraction and reflection of light

19. LEARNING OBJECTIVES List types of lenses Describe the image formed by a lens. 3. Lenses Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

20. Read textbook page 12 to learn the different types of lenses Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development https://www.liveworksheets.com/vz1372994lb

21. O: Center of lens (optical center) F: Focus, f : Focal length distance between F and O. C: Center of curvature, C = 2f Parts of lenses: Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

22. Rules for ray diagrams in lenses: 1) Rays parallel to the principal axis will refract, passing through the focal point . 2) Rays passing through the center of the lens ‘O’ will continue in a straight line . 3) Rays passing through the focal point will refract parallel to the principal axis. Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

23. Rules for ray diagrams in lenses: Use the worksheet to practice drawing the image formed by a lens in different positions. Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

24. Conduct demo experiment 1.3 page 13 from textbook Use link to show how light refracts in lenses. https://ophysics.com/l12.html Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development https://www.physicsclassroom.com/Physics-Interactives/Refraction-and-Lenses/Optics-Bench/Optics-Bench-Refraction-Interactive

25. Eyeglasses Cameras Optical micro scope Eye structure Some applications to lenses Magnifying glasses Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

26. Some applications to lenses Watch the video https://www.youtube.com/watch?v=HAW_6ukFO9w to answer the questions in the next slides State the name of the two main types of telescopes. Reflecting telescopes. Refracting telescopes. Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

27. Refracting Telescope Read pages 185 and 186 from your textbook. Explain what is the main difference between the Galilean refractor and the modern refracting telescopes. Some applications to lenses Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

28. Reflecting Telescope Some applications to lenses State the 2 types of reflecting telescopes. Newtonian reflector. Cassegrain reflector. Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

29. Applications of lenses Refracting telescope Reflecting telescope use lenses. use mirrors require a much purer material Does not require a much purer material can not be made very large can be made much larger suffer more from aberrations suffer less from aberrations used more for photography. used more for astronomy Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

30. Applications of lenses The astronomical observatories are generally situated on mountaintops. Explain the reason behind this. You need to post your answer on Padlet Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

31. LEARNING OBJECTIVES Design an experiment to investigate the effect of lens distance on the properties of the image 4. Lenses experiment Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

32. Using: a candle, lens, ruler and display; or the optical box, conduct a demo experiment to find the relationship between the distance of the object from the lens ‘ d o ’ and the distance of the image from the lens ‘ d i ’ when the object is replaced at a distance larger than 2f. OR Use link to show this experiment. https://www.physicsclassroom.com/Physics-Interactives/Refraction-and-Lenses/Optics-Bench/Optics-Bench-Refraction-Interactive

33. Answer the following questions on your notebook: Outline the relationship between ‘ d o ’ and ‘ d i ’. Is this relationship valid at all positions? Justify your answer. Is the image formed in your experiment real or virtual? Explain . If the magnification of a lens is given by , calculate the magnification of the lens you are using.  

34. LEARNING OBJECTIVES Explain why and how dispersion occurs. Applications to dispersion 5. Dispersion Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

35. In this experiment y ou need: Triangular prism, white light source, power supply, slit, filters. Light dispersion in a prism: Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html

36. Stick the red filter on one side of the slit. Place the slit in front of the light source. Place the prism on a protractor sheet. Turn on the power supply and s hine the white light on the prism. Observe the angle of refraction of the red light. Repeat the experiment for other filters (yellow, green, blue) Write down your observations on the note book Light dispersion in a prism: Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

37. Stat e what happens to the light when entering a prism. Refracts State how the angle of refraction changes with the color. Red color refracts less compared to blue color . Suggest what caused this behavior. Different colors move at different speeds inside a prism . Light dispersion in a prism: Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

38. From the picture suggest a d efinition for dispersion . Light dispersion in a prism: Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development The spreading of white light into full spectrum when entering a prism

39. Explain why red light bends less than violet light. Since the index of refraction is greater for shorter wavelengths ( i . e . speed is slower ), violet light is bent the most and red the least . Explain why dispersion does not occur in picture (a). Light in (a) is monochromatic (single frequency or color) Light dispersion in a prism: Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

40. Using the pictures, suggest what two properties of light are presented in the rainbow. Explain how. Applications Rainbows are produced by refraction and total internal reflection of light . Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

41. Check your understanding: Worksheet on dispersion (MB or hardcopy) Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

42. In the graph shown, the light is passing through three different mediums. Assign which medium is air, glass, and water. ( n air = 1, n water = 1.33, n glass =1.5) Explain your answer. n 1 n 2 n 3 Check your understanding: n 3 is air, n 2 is water and n 1 is glass . The light ray refracts (bends) away from the normal when moving from medium 1 to 2. So medium 2 has less refractive index. Similar argument is made between mediums 2 and 3. Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

43. Check your understanding: From the diagram , which light ray (A or B) will undergo total internal reflection if the incident angle is gradually increased? A, since medium 1 has larger refractive index Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

44. LEARNING OBJECTIVES Describe short-sightedness and long-sightedness. The use of lenses to treat some vision problems. 6. Vision problems Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

45. Vision problems and refraction Textbook pages 24-25 Read page 16 in your textbook “structure of human eye” to identify the different parts of human eye and their functions (WS on MB) Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

46. An image is formed on the retina with light rays converging most at the cornea and upon entering and exiting the lens . Rays from the top and bottom of the object are traced and produce an inverted real image on the retin a. How eyes work Textbook pages 24-25 Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

47. (a) The nearsighted ( Short-sightedness ) ( myopic ) eye converges rays from a distant object in front of the retina ; thus, they are diverging when they strike the retina, producing a blurry image . This can be caused by the lens of the eye being too powerful or the length of the eye being too great. Require concave lens. Vision problems and refraction Textbook pages 24-25 Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

48. (b) The farsighted ( Long-sightedness ) ( hyperopic ) eye is unable to converge the rays from a close object by the time they strike the retina, producing blurry close vision . This can be caused by insufficient power in the lens or by the eye being too short. Require convex lens. Vision problems and refraction Textbook pages 24-25 Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development

49. Check your understanding: Worksheet on vision problems (MB or hardcopy) Key concept : Systems, Related concepts : Development, consequences, Global Context : Fairness and development https://ophysics.com/l16.html