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- Creator:
- Hoeling, Barbara
- Description:
- We know that not only a plane mirror produces an image of an object in front of it – a convex spherical mirror does, too! Just look at the back of a metal spoon if you don't believe it! This interactive animation shows you how such an image arises, and how its position and size can be found. Use your mouse to move the object, the candle, along the optical axis, and observe how the position and size of its image change. You can also explore how the image is constructed, by turning on and off the principal rays. These are the three special rays that are used for the construction of the image. The first one is parallel to the optical axis and is therefore called the P-ray. It is reflected as if it came from the focal point of the mirror. The second one is the one that goes through the center of the sphere, the C-ray, which is reflected back into itself. The third is the F-ray, which would go through the focal point and is reflected parallel to the optical axis. The image of the tip of the candle is the point where these rays meet (or seem to meet) after they were reflected. It might not come as a surprise that the image of the candle is actually located behind the convex mirror, so it's a virtual image. The reflected rays to not actually meet at the position of the image, they just emerge from the mirror as if they came from there. Of course, that's the same as with a plane mirror. But you'll notice that there is also a difference: the image of a plane mirror is the same size as the object, while for a convex mirror, the image is always smaller than the object.
- Resource Type:
- Learning Object
- Identifier:
- PHY 122
- Campus Tesim:
- Pomona
- Department:
- Physics & Astronomy Department
- Creator:
- Stevens, Christy
- Description:
- This tutorial will help you to identify the relationship between your thesis and your sources and will help you practice selecting quality evidence that supports your argument. To play this file, download the ZIP archive, decompress it, and click on the "main.swf" object. All other objects in the ZIP archive are supporting flash files for that "main.swf" object.
- Resource Type:
- Learning Object
- Campus Tesim:
- Pomona
- Department:
- University Library
- Creator:
- Stevens, Christy
- Description:
- This information literacy tutorial helps students to understand the difference between scholarly vs. popular resources, what scholarly books and articles are, and how to effectively evaluate sources. To play this file, download the ZIP archive, decompress it, and click on the "main.swf" object. All other objects in the ZIP archive are supporting flash files for that "main.swf" object.
- Resource Type:
- Learning Object
- Campus Tesim:
- Pomona
- Department:
- University Library
- Creator:
- Hoeling, Barbara
- Description:
- Here you can see what is called a principal ray diagram. We have constructed the image of the candle from the three principal rays, as we explained before. This interactive animation allows you now to move the object relative to the lens, and to observe what happens to the image. Click on the object, the candle on the left, and drag it to different positions. The three principal rays are always constructed the same way: one goes straight through the middle of the lens, one goes parallel to the optical axis, and then through the focal point, and one goes through the focal point between the object and the lens, and leaves the lens parallel to the optical axis. Take some time moving the object back and forth, and try to answer the following questions: What happens to the position of the image when you move the object closer to the lens? What happens to the size of the image when you move the object closer to the lens? You will notice that the animation does not allow you to move the object closer than about two focal lengths to the lens. That's because we are trying to simulate the situation for our eye: Everything we look at is a lot further away from our eye than the size of our eyeball, which is about one inch in diameter. We'll come back to this in a moment. For now, make sure that you also observe what happens when you move the object further and further away from the lens. Where does the image move? Remember what we concluded from our experiment in the video about the position of the image of a very far away object? Is this consistent with the result of this simulation?
- Resource Type:
- Learning Object
- Identifier:
- PHY 122, PHY 131
- Campus Tesim:
- Pomona
- Department:
- Physics & Astronomy Department
- Creator:
- Hoeling, Barbara
- Description:
- This cartoon shows you a marching band, walking from an area of solid ground where the musicians can walk fast, into a region of muddy ground where they have to walk more slowly. Each row of musicians carries a long pole. Watch what happens when the first person of a row enters the muddy ground: the direction of the pole changes lightly. As more marchers of the same row come to the muddy ground, the pole rotates further. The only reason for this change in direction is the fact that the people walk at different speeds on the solid and muddy grounds. Interesting, isn't it? You can try this out yourself with some friends by marching in a row, holding a meter stick. This analogy can explain how the kink in the light ray comes about when the light enters a medium of different index of refraction, i.e., a region where its speed of propagation is less. The pole along the row of marchers symbolized the wave front, and the light beam propagates perpendicular to this wave front. As the wave front changes direction because of the different speeds of light in the different media, so does the light beam. And that's how light beams get kinks when you shine then at an angle from one medium into another: simply because light propagates with different speeds in different media. The speed of light in a medium is given by c/n, where n is the index of refraction of the medium. So you can see that the higher the index of refraction of a medium, the slower light moves in that medium.
- Resource Type:
- Learning Object
- Identifier:
- PHY 122
- Campus Tesim:
- Pomona
- Department:
- Physics & Astronomy Department
- Creator:
- Selco, Jodye I.
- Description:
- This is a simulation for chemical kinetics and equilibrium including a simulation modeling the dependence of a one-way reaction as an introduction, a simulation showing chemical kinetics conversions, and a simulation showing chemical equilibrium conversions. To play this file, download the ZIP archive, decompress it, and click on the "index.html" file in the unzipped folder. All other objects in the ZIP archive are supporting flash files for that "index.html" object.
- Resource Type:
- Learning Object
- Campus Tesim:
- Pomona
- Department:
- Center for Excellence in Mathematics and Science Teaching (CEMaST)
- Creator:
- Hoeling, Barbara
- Description:
- In this interactive animation, you can explore how the lens of the eye adjusts its thickness. This allows you to see an object in focus as it is moved to different distances from the lens. Drag the object to another position and observe how the lens changes. When you are looking at a very far away object, the lens of your eye is as thin as it can get, that means the ciliary muscle around your lens is relaxed. When you want to look at a closer object, your brain signals to the ciliary muscle to contract. This makes the lens thicker, which means its focal length becomes shorter. This way, the image is always located at the retina, and you see things in focus, no matter whether they are far or close. Keep playing with the animation and observe what happens! Try to answer the following questions: When you bring the object from far away closer, what happens to the size of the image? To the position of the image? To the shape of the lens? To the focal points of the lens?
- Resource Type:
- Learning Object
- Identifier:
- PHY 131
- Campus Tesim:
- Pomona
- Department:
- Physics & Astronomy Department
- Creator:
- Hoeling, Barbara
- Description:
- We have seen in the last video that a convex lens indeed makes an image of our object, the little lit arrow. But how exactly is this image formed? This animation shows you that light rays are going off in all directions from every point of the object. Let's look at one specific point of the object, say the very tip of the arrow. We know that the lens makes all light rays that are coming from this one point converge in one other point, the image of the tip of the arrow. But how do we know where this image point is located? There are three special rays for which we actually know the path. These three rays are called the principal rays. The first one is the one that hits the lens in the middle and goes right through without changing direction. The second one is the ray that goes parallel to the optical axis, so it hits the lens right on, the same way the sun rays hit it in the first experiment. Of course we know where such a ray goes: through the focal point! Now we can see where the image point of the tip of the arrow is located: at the intersection of these two principal rays! We can draw in a third principal ray just for confirmation: A ray that goes through the focal point of the lens leaves the lens parallel to the optical axis. And indeed, this ray also crosses with the two others in the same point! We can now find the image point for every point of the object in the same way - we can construct our image. What we find for the configuration that is shown here is: The image is smaller than the object, the original arrow, and it is upside-down, just as we observed in the video. So for this particular distance between the object and our lens, we are getting a reduced, inverted image.
- Resource Type:
- Learning Object
- Identifier:
- PHY 122, PHY 131
- Campus Tesim:
- Pomona
- Department:
- Physics & Astronomy Department
- Creator:
- Hoeling, Barbara
- Description:
- This interactive animation is very similar to the one with the convex lens you have used before. Here, too, you can click on the object and drag it to different positions, so you can observe what happens to the image. But now, you are able to move the object not only up to the focal point, but even closer to the lens. Look what happens when the object passes the focal point! Suddenly, the real image is gone, and a virtual, enlarged image appears instead as soon as the object gets closer to the lens than the focal point. Again, since this is a virtual image, it is shown striped. Play with this animation until you feel you understand what happens. Make sure you are able to answer the questions: For what object distances does a convex lens produce a real image? For what object distances a virtual image?
- Resource Type:
- Learning Object
- Identifier:
- PHY 122
- Campus Tesim:
- Pomona
- Department:
- Physics & Astronomy Department
- Creator:
- Hoeling, Barbara
- Description:
- This interactive animation demonstrates how the focal length of a lens changes with its thickness. Like in the previous slide, the lens is shown from the side, and light rays are coming in from the left. Click on the arrows on the lens and pull to make the lens longer and thinner, or squeeze it to make it shorter and thicker. Then observe what happens to the focal point. Keep playing with the animation for a little bit. This squeezable lens in the animation is actually a model for the lens in your eye, which is surrounded by a muscle, called the ciliary muscle. When this muscle contracts, it squeezes the lens of the eye, which is made of elastic fibers: The lens gets thicker. You should now be able to answer the question: How does the focal length of the eye change when the ciliary muscle contracts? – We have seen how a convex lens bundles the light rays that are coming in from very far away. But a lens can do much more than that: It can actually produce an image of a bright object!
- Resource Type:
- Learning Object
- Identifier:
- PHY 131
- Campus Tesim:
- Pomona
- Department:
- Physics & Astronomy Department