about lens glasses.D. Concepts 2. Motivation 1. Lens- A glass or a. Give the students a triviaother transparent Did you know the ancient Greeks usedsubstance so shaped spherical glasses to burn objects?that it will refract thelight from any object b. Pose the following questionsand form a real or 1. Why did the Greeks use a spherical glassvirtual image. filled with water to burn things? 2. Convergent Lens- A - Because water filled spherical glassconvergent lens is concentrates light into a single point.thicker at the center Concentrating light to a single point causes heat,and thinner at the consequently causes burning.edges. It magnifies the 2. Could we use the materials in the activityobject being seen if it is done earlier as burning glasses too? Are theynear the object. practical to use? What is much better to use?Convergent Lenses are - Yes, we could use these materials asnamed so because they burning glasses but they aren’t practical to useunite refracted light since they are hard to carry. A more practicalrays at one point. This object to use is the lens.is true because they arethicker at the center B. Presentationand thinner at theedges. 1. Present the definition of lens and its two 3. Divergent Lens- classifications through a power point.Divergent lenses arethinner at the center Lensesand thicker at its edges. A glass or other transparentIt often creates a substance so shaped that it willdiminished image of refract the light from any objectthe object when looked and form a real or virtual image.through upon this kindof lens. They are named Convergent Lens Divergent Lensdivergent lens because Lenses having a Lenses having athey diverge light rays. convex surface concave surface 4. Principal Axis- Thisis the line that is drawn 2. Present an activity 1 using real convergentthrough the centers of lens which is done by group.curvature of both a. Feel the lens. Observe what region of the
spherical surfaces. lens feels thicker and thinner. 5. Focal Point- b. Look at your pair through the lens. MakePortion where a beam sure you get a good clear view of you partner.of light parallel to the c. Pose the questionsprincipal axis 1. What did you observe?converges. - This lens is thicker at the center than at 6. Focal Length- This the edges. When we looked at our pair, the imageis the distance between was magnified.the center of the lens 2. What type of lens is this?and its focal point. - This lens is a Convergent lens. 7. Focal Plane- This isthe area that covers all 3. Discuss the characteristics and properties of athe points above and Convergent Lenses through a picture analysis of abelow the principal convergent lens.axis. 8. Image formation:Convergent Lens:a. A ray parallel to theprincipal axis isrefracted to passthrough the focal point.b. A ray that passesthrough the center ofthe lens passes through A convergent lens is thicker at the centerundeflected. and thinner at the edges. It magnifies thec. A ray that passes object being seen if it is near the object.through the focal point Convergent Lenses are named so becauseof the lens is refracted they unite refracted light rays at oneparallel to the principal point. This is true because they are thickeraxis. at the center and thinner at the edges.Divergent Lens:a. A ray parallel to the 4. Give activity 2 using real divergent lens whichprincipal axis is is done by group.refracted as though it a. Follow the procedure that was donecomes from the focal during the first activity but use the second lenspoint. instead of the first one.b. A ray that seems to b. Pose the questionscome from the focal 1. What did you observe when you usedpoint of the lens is the lens?deflected parallel to the - The image formed is diminished and it
Principal axis. thinner in the center than the edges.c. A ray that passes 2. What lens is this?through the focal point - This lens is a Divergent lens.of the lens is refractedparallel to the principal 5. Discuss the characteristics and properties of aaxis.E. Skills 1. Observing skillsfrom inferring thecharacteristics of aConvergent andDivergent lens. 2. Analyzing the Divergent lens through a picture analysis of adifferent observations divergent lens.to devise the propertiesand characteristics of Divergent lenses are thinner at the centerlenses. and thicker at its edges. It often creates a diminished image of the object whenF. Values looked through upon this kind of lens. They 1. In union there is are named divergent lens because theystrength. diverge light rays. 2. Appreciating thevalues of lenses in eye 6. Present activity 3 using a convergent lens.defect correction in the a. Using the convergent lens, view youractivity "Finding which partner through it at the level of your arm chair.Lens to what Eye". Both you and your partner should bend down to get a good view at each other. b. Find the point where the image is the clearest. Mark that point and measure the distance it is away from your eyes. Your partner should find this point at the other side of the lens. c. Pose the following questions 1. What is the distance that you measured for both sides? Are they the same? - The distance is about 4- 5 cm.
7. Present the discussion of the Anatomy of theLens by posting a picture of it. Principal Axis- This is the line that is drawn through the centers of curvature of both spherical surfaces. Focal Point- Portion where a beam of light parallel to the principal axis converges. Focal Length- Distance between the center of the lens and its focal point. Focal Plane- This is the area that covers all the points above and below the principal axis. 8. Give the rules of Image formation by lensesthrough an interactive discussion and a game. a. Give the students the following materials a.1. 3 arrows a.2. Schematic lens diagram model of aConvergent and Divergent lens a.3. Dotted Lines a.4. Letter markers b. Present the diagram of each rule of imageformation after each rule is stated. b.1. Present the rules of Image formationfor a convergent lens 1. A ray parallel to the principal axis is refracted to pass through the focal point. 2. A ray that passes through the center of the lens passes through undeflected. 3. A ray that passes through the focal point of the lens is refracted parallel to the principal axis.
b.2. Present the rules of Image formation fora Divergent lens through an interactivediscussion. 1. A ray parallel to the principal axis is refracted as though it comes from the focal point. 2. A ray that seems to come from the focal point of the lens is deflected parallel to the Principal axis. 3. A ray that passes through the center of the lens passes through undeflected.C. Application 1. Post pictures about people having the eyedefects Myopia and Hyperopia then presentquestions about the comic strip.
a. What does the pictures shows? - The picture shows people readingdifferently than normal. b. What is wrong with them? - These people have the eye defect Myopiaand Hyperopia. 2. Discuss Myopia and Hyperopia throughshowing pictures of eyeballs depicting these eyedefects. Myopia is also called as near sightedness. Myopia is either acquired or genetic. We acquire Myopia as we age. Myopia is genetically transferred from parent to offspring. It occurs when the eyeball is longer than normal, thus the image formed is formed before the retina. This defect could be corrected using an eye glass. Hyperopia is called as far sightedness. Hyperopia is genetic in nature. It occurs when the eye ball is shorter than normal, thus the image is formed beyond the retina. Like Myopia, it could also be corrected by an eye glass. 3. Give the activity “Finding which Lens to whatEye” through giving its instructions
Find out which lens is needed to correct the mentioned eye defects by applying the principles of image formation. Given a schematic model of a myopic and hyperopic eye, try to create a ray diagram using the given rays and dotted lines. Try to let the image fall on the retina of the eye model. Once you have determined what lens correct what eye defect, write your answers on a ¼ sheet of pad paper. a. Pose the following questions 1. What lens is used to correct Myopia? Howabout Hyperopia? - A convergent lens is used to correctfarsightedness and a divergent lens is used tocorrect nearsightedness. 2. How do lenses correct these eye defects? - These lenses either converges or divergeslight rays before entering the eye’s lens. Thismakes the image form on the eye’s retina. 3. Are lenses important? How? - Lenses are important. They are used tohelp people with eye defects. They correct eyedefects like Myopia and Hyperopia.Generalization 1. Post a Comic Strip about lenses. Oh my! Where are my glasses?
2. Pose the following questions 1. What is the comic strip all about? - It shows the character Velma trying tofind her glasses. 2. What are eyeglasses? Expound on youranswer. - Eyeglasses are lenses. Lenses are glassesthat are used to refract light. There are two typesof lenses, divergent and convergent lenses.The first one is used to scatter light waves and thelatter is used to converge light to one point. 3. How do lenses help correct eye defects?What is the principle behind it? - These lenses either converges or divergeslight rays before entering the eye’s lens. Thismakes the image form on the eye’s retina. Lensesuse the principle of image formation. 4. What is the importance of lenses? - Lenses are important to people sufferingfrom eye defects. They correct eye defects so theperson could appreciate the world. Also, they letus appreciate the world around us and let us seethings that the eye couldn’t normally see.