Gizmos Name: Date: Ray Diagrams with Lenses Gizmo Warm-up The Ray Tracing (Lenses) Gizmo shows light rays passing through a lens. The light rays are bent by refraction as they pass through the lens and form a focused image to the right of the lens. To begin, turn on the Colorize lines checkbox. Under Show lines, turn off the Central line and the Line through 25.0 -200 -15.0 -10.0 -50 focal point so that only the Parallel line is showing. 1. The blue dots in front of and behind the lens are the focal points of the lens. Move the candle on the left back and forth and up and down. What is always true about the light ray that emerges from the right side of the lens? 2. Turn off the Parallel line and turn on the Line through focal point. Move the candle. What do you notice about this line? A convex lens is called a "converging lens" because it focuses light rays into a point. A real image is formed where the light rays emitted from a point converge on the other side of the lens. If you placed a sheet of paper at the image, a focused image would be projected onto the paper. Question: How do lenses create images? 1. Observe: In its current configuration, the distance from the candle to the focal point is 12 units and the distance from the focal point to the lens is also 12 units. What do you notice about the orientation and size of the candle's image on the right side of the lens? 2. Investigate: Complete each action listed in the table below, and describe how that action affects the image to the right of the lens. Return the candle and focal point to their original positions (-24 for the candle, -12 for the focal point) after each action. Action Effect on image Move the candle to the left & right. Move the focus to the right & right. Reproduction for educational use only Public shoring or posting is probbuted. 2018 ExploreLearning All rights reserved3. Analyze: How is the image size related to the distance between the candle and the focus? 4. Explore: Move the candle to -12 and the focal point to -24. Shorten the candle to see the whole image. What do you notice when the candle is between the focal point and the lens? The image you see is called a virtual image because no actual light rays are focused there. The dotted lines represent locations from which light appears to be coming to an observer located left of the lens. An observer would perceive a magnified virtual image of the candle. This is what happens when you look at an object through a magnifying glass. 5. Investigate: Return the candle to -24 and the left focal point to -12. Under Show specific line segments, turn off Apparent light lines. On the menu at lower right, select Concave lens. A concave lens curves inward on both sides. A. What do you notice about the three lines after they pass through the concave lens? Because a concave lens causes light rays to spread apart, it is also called a "diverging lens." B. Turn on Apparent (or "Virtual") light lines. Is the image of the candle a real image or a virtual image? Explain. (Hint: Recall that a real image forms where light rays are focused.) C. Move the candle back and forth. No matter where the candle is placed, what is true about the image? D. What would an observer see if she looked at the candle through the concave lens? 6. Summarize: What are the differences between the images formed by convex and concave lenses? 7. Complete these two diagrams. Reproduction for educational use any Public shoring or posting is profebuted. @ 2019 ExploreLearning All rights reserved