Ch26_Demberro

= = toc = = =Chapter 26=

Lesson 1
When a ray of light reaches the end of one medium and goes into another one, the ray will bend a little bit if it is going to the other boundary at an angle. This will only occur at the boundary. When looking at an object where the light is in different mediums, the object will appear to "bend" when is in not in the middle. The most popular one is "breaking" a pencil when it is put in water, as the part of it in water looks to be in a different position from the rest of it. Refraction can only occur when light speeds up or slows down at a boundary, or else there is no real "barrier". Also, it must approach at an angle, because if it is going at it perpendicularly than it will just continue to go straight.
 * What is refraction at a boundary for light?**
 * How does refraction relate to sight?**
 * What causes refraction?**

Optical density of a material is its index of refraction. A higher index of refraction means that the light will slow down when it passes through the material. This is evident by this equation:. Because you need the light to either slow down or speed up when passing through the boundary, the two mediums must have differing index of refraction values. Using the acronyms FST and SFA, it is easier to understand that going from fast to slow moves towards the normal line of the boundary, while slow to fast moves away from the normal of the boundary. This can be imagined that when passing through the boundary, going slow to fast will make the ray "jut out" as soon as it can, thus it moves away. When going fast to slow, the ray is hindered and thus moves towards the middle.
 * What is optical density and how does it relate to refraction and speed of light through a medium?**
 * What will be the direction of the ray's bending?**

Lesson 2
There are four main numbers that determine refraction. There are the two indexes of refraction and two angles for the incidence and refracted rays. Thus, different indexes will create different angles. The equation for Snell's Law is rather simple. When three of the variables are given, simple trigonometry and use of arcsin can get the answer.
 * What are the variables of refraction?**
 * What is Snell's Law and how is it applied?**

Lesson 3 and 4
With the incidence angle part of the ray will reflect back off the medium. As the incidence increases from 0 to 90, the refracted angle gets dimmer while the reflected angle gets stronger until it is all reflection. The ray must be going from denser medium to less dense medium. Up until a certain angle, the refraction angle will be equal to 90º and only total internal reflection will be there when an angle surpasses the critical angle. It can be determined mathematically thusly:. When a light passes through both sides of a prism, ROYGBIV is shown. This occurs because violet has a shorter wavelength and thus bends at a larger angle than those closer to red. This also explains how rainbows are formed as the light passes through the mist in the air that serves as a prism.
 * What is internal reflection?**
 * What is the critical angle?**
 * How is light dispersed through a prism?**

Lesson 5
Because a lens is piece of transparent material that forms an image of an object through refraction, it has similar qualities to a mirror. There is a principal axis and focal point along it, and they can be diverging or converging (concave or convex). Also, they have a vertical axis that goes through the middle of a double lens (one that is converging or diverging from both ends). Lenses refract light in double lenses at the first and last boundary. Thus, parallel rays refract to the focal point on the opposite side through a converging lens and away from the center in diverging lens. Likewise, incident rays traveling across the focal point of a converging lens will bounce back parallel while those heading towards the focal point in diverging lens will also refract parallel. Lens form images that have similar qualities as the ones formed by the different kinds of mirrors. Converging lens can be virtual or real, like diverging mirrors, and diverging lens can be only be virtual, like convex mirrors. Both can produce images using similar ray patterns. It should be noted that a real images for lenses are on the opposite side of the lens compared to the object, and virtual images are on the same side of the lens compared to the object. One ray goes from top of image right through the center. Another goes parallel to principal axis, across the top, then goes to the focal point on the opposite end after hitting the lens. The third goes from focal point on same side as the object, past the top of the object, then hits the lens, then goes parallel to principal axis. Wherever these three intersect is where the image is produced.
 * What is the anatomy of a lens?**
 * How do lenses refract light?**
 * How do lens produce images?**
 * How do ray diagrams show where images are produced in a convex lens?**

There are five cases for pattern of images. Case 1: When object is past 2F, image is reduced, inverted, real, and between F and 2F Case 2: When object is at 2F, image is same size, at 2F on opposite side, inverted, and real. Case 3: When object is between 2F and F, it is past 2F on opposite side, magnified, and real. Case 4: When object is F, there is no image. Case 5: When object is between F and lens, image is upright, magnified, and on same side as object (virtual) between F and 2F. Essentially the same exact thing as the convex lens. Only difference is that image will always be virtual, reduced, and between F and mirror on same side. This will occur no matter where the object is. Same exact ones with mirrors. f= focal length. d= distances. M=magnification. h=heights.
 * How do ray diagrams show where images are produced in a concave lens?**
 * What are the mathematics of linses?**

Lesson 6
There is a transparent membrane called the cornea over the eye. Past that is a little opening called the pupil. The pupil can be adjusted by the iris which expands or reduces the pupil depending on how much light enters the eye. Crystalline lens are behind the iris and can change shape to adjust to images, which are attached to cillary muscles that help shape the lens. The retina is the inner surface of the eye that detect intensity and frequency of light. Finally, the nerve cells will all bundle together in the optic nerve. The cornea is shaped like a convex lens and refracts the light rays to the retina, where the image will be real, reduced in size, and inverted. This can also be explained because the eye has a generally tiny focal length (1.8 cm) compared to what it is usually looking at. Accommodation is what puts the image in the retina. Because it is reduced and real, it is then possible for the image to "fit" inside the retina. Also, the brain flips the inverted image to be right-side up. The fovea centrails are small area in charge of adjusting focusing on objects for clearer images. With help of the cillary muscles, accommodation works when the eye can make a short focal length for close objects and a long one for those far away. Therefore, the ability to change curvature allows people to focus on objects at varied lengths to produce the best images. Farsightedness is when people are unable to focus on images close to them, usually because the ciliary muscles are not strong enough to expand. Therefore, the image is placed too far down the retina and the image is not clear. This can be cured with a converging lens because light will refract before reaching the eye, thus it will refract again to properly be pinpointed at the retina. Nearsightedness is when people are unable to focus on images far away from them. This occurs when images form in front of the retina. To correct this, you need a diverging lens, which would spread out the refracted rays to the outside before meeting at the retina.
 * What is the anatomy of an eye?**
 * How does the eye form and detect images?**
 * What is accomadation?**
 * How do you correct farsightedness and nearsightedness?**