OPTICS: EXAM REVIEW

Knowledge and Understanding

1. What is a real image? 20. What type of lens produces a real image?

2. What is a virtual image? 21. What type of lens produces a virtual image?

3. Describe the law of reflection as a relationship 22. What is one use for a diverging lens? between the angle of incidence, the angle of reflection, and the normal. 23. Draw a ray diagram to show why your image is reversed in a plane mirror. 4. Describe the kinds of images that can be formed by plane mirrors. 24. How is the focal point of a mirror different from the vertex? 5. What type of mirror produces only diverging rays? 25. What are two versions of the magnification formula? 6. What type of mirror can produce both converging and diverging rays? 26. What is the definition of refraction?

7. Describe what kind of mirror you would use if you 27. Which substance refracts light more, water or glass? needed to view a large, spread-out area in a small Explain why. mirror. 28. What is the speed of light? 8. Compare the shapes of convex and concave mirrors. How are they similar, and how do they differ? 29. What is the definition of index of refraction?

9. What kind of images do convex mirrors form? 30. What is the formula for calculating the index of refraction of a material? 10. What are three uses for convex mirrors? 31. What is a common example of dispersion? 11. A lighted object is placed at the focal point of a concave mirror. Describe the light rays reflecting off 32. Define critical angle. the mirror. 33. Which will be larger: the critical angle at an air-glass 12. Describe how the positions of a mirror, incident ray, interface or the critical angle at a water-glass reflected ray, and normal are related. interface? Explain.

13. How does your image in a mirror compare with 34. State the thin lens equation. looking directly at yourself? 35. Optical devices help us see farther and more clearly 14. When is light travelling at its fastest? than we can with unaided eyes. a. List two parts of the eye that can refract light. 15. What is dispersion? b. What structure controls the amount of light that enters the eye? 16. Under what conditions can you slow down light and then speed it up again? 36. State the cause of: a. far-sightedness 17. Describe how light changes its direction when moving b. near-sightedness from one medium to another. 37. Explain why you agree or disagree with the following 18. What property of a medium is given by its index of statements. For any you disagree with, provide the refraction? correct statement. a. The normal is drawn at a 90° angle to the mirror 19. Through which medium does light pass more quickly, or lens. one with a refractive index of 2.0 or one with a b. When light is reflected from a curved mirror, the refractive index of 3.0? angle of incidence is twice the angle of reflection. Application Questions

1. A microscope produces an image that is 1.00x10–4 m 11. A virtual image is produced by a convex mirror that is high from an object that is 4.00x10–7 m high. What is 1.60 cm from the mirror. If the magnification is 0.20, the magnification of the microscope? how far from the mirror is the object?

2. A concave mirror produces an image on a wall that is 12. The speed of light in leaded glass is 1.66 x 108. What 30.0 cm high from an object that is 6.5 cm high. is the index of refraction of this type of glass? What is the magnification of the mirror? 13. The speed of light in quartz is 2.10 x 108 m/s. What 3. An object is placed 75 cm from a concave mirror. A is the index of refraction of quartz? real image is produced 50 cm away. What is the magnification? 14. The speed of light through a material is 1.24x108 m/s. What material is it? 4. A person standing 3.00 m from a glass window sees her virtual image 3.00 m on the other side. What is 15. What is the speed of light through alcohol? the magnification of the window? 16. Determine the refractive index of a medium if the 5. A camera creates a real image of a tree 40 m away. speed of light slows to 1.2 x 108 m/s. The image is formed 3.0 cm behind the lens. Find the magnification. 17. A light ray passes from a vacuum into a substance where its speed is 2.26 x 108 m/s. What is the 6. A slide projector has a magnification of 50. How wide substance? will the projected image be if the slide is 2.8 cm wide? 18. A powerful magnifying glass produces a real image 4 7. A magnifying glass will magnify 6 times. If the mm from the convex lens. If the object was placed 28 magnifying glass is held over a page and magnifies a mm away, what is the focal length of the lens? letter that is 2 mm tall, how big is the image? 19. Determine the focal length of a convex lens that 8. An insect is magnified 12 times by a concave mirror. produces a virtual image at a distance of 30 mm If the image is real, inverted, and 6 cm from the when the object is placed 15 mm away. mirror, how far away is the insect? 20. A convex lens has a focal length of 15 cm. An object 9. A lens produces a real image that is 23 times bigger is placed 20 cm from the lens. What type of image is than the object. If the object is 14 cm away, how far formed? How far from the lens is the image? away is the image?

10. A human hair is placed 3 mm from a powerful microscope lens that has a magnification of 40 times. How far from the lens will the image be formed?

Answers

1. M = 250 6. hi = 140cm or 1.40m 11. 8.0cm 16. 2.5 2. M = 4.6 7. hi = 12mm or 1.2cm 12. n = 1.81 17. 1.33, water 3. M = 0.667 8. do = 0.5cm 13. n = 1.43 18. 3.5 mm 4. M = 1 9. di = 322cm or 3.22m 14. n = 2.42, diamond 19. 30 mm 5. M = 7.5 x 10–4 10. di = 120mm or 1.2m 15. 2.21 x 108 m/s 20. larger, real, inverted, 60cm