Using Mirrors to Form Images

Transcription

1 Using Mirrors to Form Images Textbook pages Before You Read You stand in front of a. In what ways is your reflection the same as you? In what ways is your reflection different from you? Write your ideas on the lines below. Mark the Text Identify Concepts Highlight each question heading in this section. Then use a different colour to highlight the answers to the questions. reflected light rays converge at the focal point incoming light rays are parallel to one another focal point Section 5.2 Summary reflected light rays diverge so they do not meet incoming light rays are parallel to one another focal point Reading Check 1. How is a concave different from a convex? What are three common types of s? There are three common types of s: 1. A plane is a with a flat surface. You might find a plane on a bathroom wall or cabinet. 2. A concave is a that curves inward, like the inside of a spoon. A flashlight has a concave behind the bulb. Shaving s and make-up s are concave, too. 3. A convex is a that curves outward, like the outside of a spoon. Some bicycle s are convex. The large, curved s that are used for security in many stores are convex, too. 74 MHR Section 5.2 Using Mirrors to Form Images 2006 McGraw-Hill Ryerson Limited

2 Section 5.2 Summary What happens when light rays strike curved s? You learned what happens to light rays when they reflect from a plane in section 5.1. Light rays behave in a different way when they reflect from curved s. The light rays that reflect from a concave meet (converge) at a single point. This point is called a focal point because the light rays focus together there. Light rays that meet at a focal point are called converging light rays. The light rays that reflect from a convex spread out (diverge). Light rays that spread out after they reflect from a convex are called diverging light rays. continued Reading Check 2. What is the difference between light rays that are converging and light rays that are diverging? How do the images formed in s compare? All s form images of s because s reflect the light that strikes them in a regular pattern. How the image looks depends on whether the is flat or curved. Appearance of image Plane Concave (if is near the ) Concave (if is far from the ) Convex Object Object as seen in plane Object as seen in concave (near ) Object as seen in concave (farther from ) Object as seen in convex Location Size behind the same size as behind the larger than Shape same shape different shape in front of the smaller than different shape behind the smaller than different shape Left-right orientation Up-and-down orientation reversed reversed reversed reversed upright upright upside down upright 2006 McGraw-Hill Ryerson Limited Section 5.2 Using Mirrors to Form Images MHR 75

3 Applying Knowledge Section 5.2 Use with textbook pages Flat s and curved s Complete the following table describing the three different types of s. Plane Mirror Concave Mirror ( near to ) Concave Mirror ( far from ) Convex Mirror Is the reflecting surface of the flat, curved inward, or curved outward? Is the image smaller, larger, or the same size as the? Is the image upright or upside down? Is the image the same shape as the? Does the image seem to be behind the or in front of the? Draw and label one example of how this type of might be used McGraw-Hill Ryerson Limited Section 5.2 Using Mirrors to Form Images MHR 77

4 Cloze Activity Section 5.2 Use with textbook pages Mirror,, on the wall Vocabulary behind concave converging convex diverging focal point images in front plane reflect upright upside down Use the terms in the vocabulary box to fill in the blanks. Use each term only once. You will not need to use every term. 1. All s light. 2. There are three types of s. All three types reflect light rays to form. 3. A is a that is flat and smooth. It produces an image that is the same as the and appears to be the same distance from the as the. 4. A is a that curves inward. The image formed by this type of depends on how far away the is from the. 5. Light rays that come together at a focal point are described as. 6. If the is far from the concave, its image is small and. 7. If the is close to a concave, then the image appears to be larger than the and is. 8. A is a that curves outwards. It reflects parallel light rays as if they came from a focal point the. 9. Light rays that spread apart after reflecting are described as. 78 MHR Section 5.2 Using Mirrors to Form Images 2006 McGraw-Hill Ryerson Limited

5 Assessment Section 5.2 Use with textbook pages Using s to form images Match each Term on the left with the best Descriptor on the right. Each Descriptor may be used only once. Term 1. diverging 2. converging 3. plane 4. convex 5. concave Descriptor A. spreading apart B. coming together C. curves inwards D. curves outwards E. is smooth and flat F. point where light rays meet Circle the letter of the best answer. 6. Which of the following is used to make an image that is the same size as the? A. plane B. convex C. concave D. both concave and convex s 7. What do all three types of s have in common? A. they all produce upside down images B. they all reflect light rays to form an image C. they all reflect light rays so that the rays diverge and do not meet D. they all reflect light rays so that the rays converge on a focal point 8. What type of image would you expect to see if you looked at yourself in the bowl of a spoon? A. an upright, larger image of yourself B. an upright, smaller image of yourself C. an upside down, larger image of yourself D. an upside down, smaller image of yourself 9. Which of the following s can produce an upright image? I. plane II. III. convex concave A. I and II only B. I and III only C. II and III only D. I, II, and III 10. Which of the following s can be used to make you look taller? A. plane B. convex C. concave D. both convex and concave s 11. Which of the following statements is incorrect about a plane? A. It reverses left and right. B. It produces an image in front of the. C. It produces an image that is the same size as the. D. It produces an image that appears to be the same distance from the as the McGraw-Hill Ryerson Limited Section 5.2 Using Mirrors to Form Images MHR 79

6 Using Lenses to Form Images Textbook pages Section 5.3 Summary Before You Read Many common devices, such as eyeglasses and magnifying glasses, have lenses. What are lenses used for? Record your ideas in the lines below. State the Main Ideas As you read this section, stop after each paragraph. Put what you have just read into your own words. incoming light rays concave lens refracted light rays are diverging What is a lens? A lens is a piece of transparent material that is curved so that light rays will refract as they pass through it. The more curved the sides of a lens are, the more a ray of light will refract as it passes through the lens. There are two types of lenses: concave and convex. Reading Check 1. What happens to light rays that pass through a concave lens? What is a concave lens? A concave lens is thinner in the middle and thicker at the edges refracts light rays that pass through it away from the normal. The light rays diverge and do not meet at a focal point. forms images that are upright forms images that are smaller than the 80 MHR Section 5.3 Using Lenses to Form Images 2006 McGraw-Hill Ryerson Limited

7 Section 5.3 Summary What is a convex lens? A convex lens is thicker in the middle and thinner at the edges. refracts light rays that pass through it toward the normal. The light rays converge at a focal point. The image formed by a convex lens depends on how far the is from the focal point. The distance from the centre of the lens to the focal point is called the focal length. If an is between the lens and the focal point (less than one focal length), the image is upright and larger than the. If an is more than one focal length away from the lens, the image is upside down and smaller than the Distance of an from the convex lens How the image compares with the continued Reading Check 2. What is the focal length of a lens? more than two focal lengths between one and two focal lengths directly at the focal point less than one focal length upside down and smaller upside down and larger no image forms upright and larger convex lens focal length incoming light rays focal point 2006 McGraw-Hill Ryerson Limited Section 5.3 Using Lenses to Form Images MHR 81

8 Applying Knowledge Section 5.3 Use with textbook pages Concave lenses and convex lenses Compare and contrast concave lenses and convex lenses. Lenses Concave Convex Draw the lens. Do light rays converge or diverge? Is the image upright or upside down? Is the image smaller or larger than the? 2006 McGraw-Hill Ryerson Limited Section 5.3 Using Lenses to Form Images MHR 83

9 Assessment Section 5.3 Use with textbook pages Using lenses to form images Match the Term on the left with the best Descriptor on the right. Each Descriptor may be used only once. 7. Which of the following is a concave lens? A. C. B. D. Term 1. lens 2. focal length 3. convex lens 4. concave lens Descriptor A. point where the converging light rays meet B. a piece of transparent material that bends light C. lens that is thinner in the middle than at the edge D. lens that is thicker in the middle than at the edge E. distance from the centre of the lens to the focal point Circle the letter of the best answer. 5. What happens to the light rays that pass through a convex lens? A. all the light rays diverge B. all the light rays converge C. all the light rays are absorbed by the lens D. some light rays diverge and some light rays converge 6. Describe the image that is produced by a concave lens. A. it is upright and larger than the B. it is upright and smaller than the C. it is upside down and larger than the D. it is upside down and smaller than the 8. A concave lens reflects light rays A. towards the normal B. away from the normal C. along the normal D. none of the above 9. A convex lens reflects light rays A. towards the normal B. away from the normal C. along the normal D. none of the above 10. Light rays converge A. at the focal length B. at the focal point C. inside the lens D. on the edge of the lens 11. If the is more than two focal lengths from a convex lens, the image will be A. upside down and smaller B. upside down and larger C. upright and larger D. no image forms 2006 McGraw-Hill Ryerson Limited Section 5.3 Using Lenses to Form Images MHR 85