Chapter+25

flat =Chapter 25 Guiding Questions=

Refraction Summaries
=Lesson 1: Refraction at a Boundary=

Reflected pulse - it is part of a pulse that hits off of a boundary and reflected back Transmitted pulse - it is part of a pulse that continues right through the boundary
 * What is reflected pulse and transmitted pulse?**

When a light wave hits a boundary separating two different mediums, the path of light bends. This is known as refraction.
 * What is the refraction of light waves?**

When light is shown through two mediums, visual distortion could occur. Light travels at a straight line, but when it hits a boundary, the ray travels in a different straight path. To the eye, this can cause something to look like it is in two different places.
 * How does refraction cause visual distortion?**

The light wave changes directions, speeds up or slows down, and increases or decreases its wavelength when it crosses a boundary. Light refracts at a boundary because of a change in speed. The light has to hit the boundary at an angle.
 * What causes refraction?**

Optical Density - tendency of atoms of a material to maintain the absorbed energy of an electromagnetic wave in the form of vibrating electrons before reemitting it as a new electromagnetic disturbance Index of Refraction Value - a number that indicated the number of times slower that a light wave would be in that material than it is in a vacuum. If a ray of light passes across the boundary from a material in which it travels fast into a material in which travels slower, then the light ray will bend towards the normal line. If a ray of light passes across the boundary from a material in which it travels slowly into a material in which travels faster, then the light ray will bend away from the normal line. Of all the possible paths that light might take to get from one point to another, it always takes the path that requires the least amount of time.
 * What is the optical density and index of refraction value of a material?**
 * Describe the direction of bending during refraction.**

=Lesson 2: The Mathematics of Refraction=

The top angle is the angle of incidence and the bottom one is the angle of refraction. Snell's Law is used to determine the angles of refraction and incidence or the indices of refraction given certain numbers. It can predict in which direction light will travel after passing through a boundary.
 * Show a diagram on refraction.**
 * What is Snell's Law?**

=Lesson 3: Total Internal Reflection= Yes, the rules of refraction and reflection still apply.
 * Can reflection and refraction occur at a boundary?**

It is the reflection of the total amount of incident light at the boundary between two media. Instead of light being refracted through the boundary, all of the light is reflected off. There are two requirements for total internal reflection which are that the light is in the more dense medium and approaching the less dense medium and that the angle of incidence is greater than the critical angle.
 * What is total internal reflection?**

It is defined as the angle of incidence that provides an angle of refraction of 90 degrees. When the angle of incidence is greater than this, total internal reflection occurs.
 * What is the critical angle?**

=Lesson 4: Interesting Refraction Phenomena=

When a light wave travels through a prism, there are many different index of refraction values for each frequency of light. Violet light travels slower through the prism than red light because of this fact. So violet light refracts more than red light. When the light enters the boundary, there is a separation of light white light into colors of the spectrum. Upon exiting the separation becomes even greater and ROYGBIV can be observed.
 * How does dispersion of light through prisms occur?**

The amount of overall refraction caused by the passage of a light ray through a prism is often expressed in terms of the angle of deviation. It is the angle made between the incident ray of light entering the first face of the prism and refracted ray that emerges from the second face of the prism. The angle of deviation varies with wavelength. Shorter wavelengths (BIV) will be deviated more form their original path.
 * What is the angle of deviation?**

Each tiny droplet of water acts as a tiny prism that both disperses light and reflects it back to your eye. The picture below shows what happens inside each droplet.
 * How do rainbows form?**

A mirage is an optical penomenon that creates the illusion of water and results from the refraction of light through a non-uniform medium.
 * What is a mirage?**

=Lesson 5: Image Formation by Lenses=

A lens is a piece of transparent material that refracts light rays in such a way as to form an image.
 * What is a lens and what are the types?**

Any incident ray traveling parallel to the principal axis of a converging lens will refract through the lens and travel through the focal point on the opposite side of the lens. Any incident ray traveling through the focal point on the way to the lens will refract through the lens and travel parallel to the principal axis.
 * How does refraction by a converging lens work?**

Any incident ray traveling parallel to the principal axis of a diverging lens will refract through the lens and travel in line with the focal point (i.e., in a direction such that its extension will pass through the focal point). Any incident ray traveling towards the focal point on the way to the lens will refract through the lens and travel parallel to the principal axis.
 * How does refraction by a diverging lens work?**


 * Image Formation by a Converging Lens**


 * Image Formation by a Diverging Lens**

Using a straight edge, accurately draw one ray so that it passes exactly through the focal point on the way to the lens. Draw the second ray such that it travels exactly parallel to the principal axis. Draw the third incident ray such that it travels directly to the exact center of the lens. Place arrowheads upon the rays to indicate their direction of travel. The ray that passes through the focal point on the way to the lens will refract and travel parallel to the principal axis. Use a straight edge to accurately draw its path. The ray that traveled parallel to the principal axis on the way to the lens will refract and travel through the focal point. And the ray that traveled to the exact center of the lens will continue in the same direction. Place arrowheads upon the rays to indicate their direction of travel. Extend the rays past their point of intersection. The point where they intersect is the top of the object.
 * How to draw ray diagrams for lenses**


 * What are the mathematics behind lenses?**

=Lesson 6: The Eye=


 * What is the anatomy of the eye?**

The ability of the eye to adjust its focal length is known as accommodation. Since a nearby object (small dobject) is typically focused at a further distance (large dimage), the eye accommodates by assuming a lens shape that has a shorter focal length. This reduction in focal length will cause more refraction of light and serve to bring the image back closer to the cornea/lens system and upon the retinal surface. So for nearby objects, the ciliary muscles contract and squeeze the lens into a more convex shape. This increase in the curvature of the lens corresponds to a shorter focal length. On the other hand, a distant object (large dobject) is typically focused at a closer distance (small dimage). The eye accommodates by assuming a lens shape that has a longer focal length. So for distant objects the ciliary muscles relax and the lens returns to a flatter shape. This decrease in the curvature of the lens corresponds to a longer focal length.
 * What is accomodation?**
 * What is farsightedness and how is it corrected?**


 * What is nearsightedness and how is it corrected?**