Ch24LevineE

Chapter 24 Guiding Questions
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a. __Newton__- investigated the refraction of light, demonstrated that a prism could decompose white light into a spectrum of colors b. __Huygens__- thought light was made of waves vibrating up and down perpendicular to the direction that light travels, became known as "Huyugens' Principle" c. __Grimaldi-__ accurately observed the diffraction of light d. __Young-__ studied the interference of light waves by shining light trough a screen with two slits equally separated e. __Maxwell-__ showed that magnetism, electricity, and light were all part of the electromagnetic field f. __Hertz-__ discovered radio waves, frequency of waves is named after him g. __Einstein-__ suggested that light is composed of tiny particles called photons, and each photon had energy
 * 1. Identify the contributions from each of the following scientists to the study and the nature of light.**

a. __Galileo-__ found that light travelled faster than sound but was unable to find the exact speed b. __Roemer-__ made the first quantitative measurement of light speed, found the ratio of the speed of light to the speed with which earth orbits the sun c. __Fizeau-__ found that light travels at 3.13 x 10^8 m/s.
 * 2. Measuring the speed of light was challenging. Describe the results of the experiments by each of the following scientists.**

a. Electromagnetic waves do not require a medium to travel, and mechanical waves do b. Electromagnetic waves are 3 dimensional, mechanical waves are 2 dimensional
 * 3. What are the 2 biggest differences between an electromagnetic wave and a mechanical wave?**

a. visible light is in the middle, it is what we can see b. radio waves--> microwaves-->infrared rays-->visible light-->ultraviolet rays-->x-rays-->gamma rays c. wavelength decreases from left to right d. frequency increases from left to right e. electromagnetic spectrum (from left to right) ROYGBIV
 * 4. Describe the EM spectrum.**

a. light waves have frequency, so we can compare the observed frequency to the actual frequency using the equation for the Doppler effet
 * 5. Apply the Doppler affect to light.**

a. the conversion of unpolarized light to polarized light b. a measurement of the electromagnetic field's alignment
 * 6. What is polarization?**

a. States that the intensity produced when a polarizer and analyzer are placed in front of an incident beam is equal to the original intensity times the cosine squared of the angle between the two filters.
 * 7. Describe Malus' Law.**

a. __Polarizer__ is always the first filter and removes 50% of light's intensity b. __Analyzer-__ is always the second filter, the amount of intensity it removes is dependent upon the angle between the first and second filter
 * 8. Contrast the polarizer and the analyzer.**

a. When light reflects off of shiny surfaces b. When light enters the earth's atmosphere
 * 9. When does polarization occur in nature?**

a. What is the relative orientation of the transmission axes of the filters when maximum intensity is transmitted? i. 0 degrees b. What should the intensity of the light beam be in this orientation? i. S= So(costheta)^2 S=820/2 S= 410 W/m^2 c. What is the relative orientation of the transmission axes of the filters when minimum intensity is trasmitted? 90 degrees d. What will be the intensity of the light transmitted by the filters when the intensity is at a minimum i. 0 W/m^2 e. If a third polarizer is inserted between the first two polarizers (as oriented in c) and the angle of this third polarizer is rotated until the angle between it and the first polarizer is 25 degrees. What will be the intensity transmitted by all three? i. S=So(costheta)^2 S= 510 cos^2(25) S= 337 W/m^2
 * 10. Two polarizing filters are placed in the path of a beam of light with an intensity measured to be 820. W/m^2. The analyzer is then rotated**
 * until the intensity is at a maximum. Assuming that the two filters are perfect:**

S= 337cos^2(65) S= 60 W/m^2

Chapter 25 Guiding Questions
a. Wave fronts are surfaces that all emit light through the same medium b. Rays are single beams of light
 * 1. Distinguish between wave fronts and rays.**

a. Specular reflection occurs off of smooth surfaces ex. mirrors, paper b. Diffuse reflection occurs off of rough surfaces, ex. pavement
 * 2. Distinguish between specular and diffuse reflection.**

a. Light reflects in such a way that the reflected angle is the same as the incidence angle
 * 3. What is the law of reflection?**


 * 4. Draw a diagram identify rays and angles.**

a. n1sin(theta)1=n2sin(theta)2 1sin30=1.65sin(theda)2 theta2= 17.64 degrees
 * 5. A ray of light in air is incident on an air-to-glass boundary at an angle of 30 degrees with the normal. If the index of refraction of glass is 1.65, what is the angle of the ray reflected off the glass surface with respect to the normal?**

a. location b. orientation c. size d. type
 * 6. List the 4 ways we describe images. In other words what are the characteristics of images?**

a. Real images occur when light rays intersect, and the image will be located in front of the mirror b. Virtual images occur when light rays do not actually intersect, and the image will be located behind them mirror
 * 7. Distinguish between real and virtual images.**

a. How much bigger or smaller the image is in comparison to the object.
 * 8. What is magnification?**

a. Behind mirror b. Upright c. Same Size d. Virtual
 * 9. What are the image characteristics of an object viewed in a plane mirror?**

a. the mirror or the lens (vertex)
 * 10. What is the reference position for all distances measurements on mirror or lens problems?**

a. __Concave Mirrors-__ are diverging, have a positive focal length, spread light, produce real AND virtual images based on the location of the object b. __Convex Mirrors-__ are converging, have a negative focal length, focus light, produce only virtual images
 * 11. What is the sign convention for images in mirrors or lenses?**
 * 12. Distinguish between concave and convex mirrors.**

a. __Principal Axis-__ goes through the center of the mirror and has C and F along it b. __Focal Point-__ Point where all the rays reflect to off mirror c. __Focal Length-__ Distance between the mirror and the focal point d. __Center of Curvature-__ radius of a spherical mirror if mirror was part of a full circle e. __Radius of Curvature-__ twice the focal length, distance from center of curvature to mirror
 * 13. Identify the following terms:**

a. reduced b. virtual c. upright
 * 15. What are the image characteristics of an object viewed in a convex mirror?**

a. No object will be found
 * 16. WHat image will be produced when the object viewed is located at the focal point of the mirror?**

a. Makeup mirrors are concave mirrors and are used to produce magnified images so makeup can be applied carefully b. Car Mirrors are convex mirrors and are used to focus images so a wider rear view is seen
 * 17. What are several applications of mirrors (besides looking at your own gorgeous features)?**

Pre-Lab Assignment
a. There is a direct relationship between the intensity of light and the cosine squared of the angle. a. I predict my hypothesis based on Malus' Law which states that a. We will use polarizers, a light sensor, and a light source. We will shoot a beam of light through two polarizers (varying the angles between them) and will measure the resulting intensity of light. Between Fliters (degrees) || Intensity of Light (W/m^2) || a. Maximum intensity when the angle between the filters is 0 degrees. b. Minimum intensity when the angle between the filters is 90 degrees. a. The intensity of transmitted light is inversely proportional to the angle between the polarizers between 0 and 90 degrees.
 * 1. The object is state in the title. What is your hypothesis?**
 * 2. What is the rationale for your hypothesis?**
 * 3. How do you think you might test this hypothesis? (What might you measure and how?)**
 * 4. Read the procedure and calculations. Make any tables in order to organize your data and calculations.**
 * Angle
 * 5. Light is shown through a set of 2 polarizing filters. When is transmitted light at a maximum intensity? Minimum intensity?**
 * 5. Light is shown through a set of 2 polarizing filters. When is transmitted light at a maximum intensity? Minimum intensity?**
 * 5. Light is shown through a set of 2 polarizing filters. When is transmitted light at a maximum intensity? Minimum intensity?**
 * 5. Light is shown through a set of 2 polarizing filters. When is transmitted light at a maximum intensity? Minimum intensity?**
 * 6. What is the relationship of the intensity of transmitted light to the angle of the polarizers between 0 and 90 degrees?**

Reflection Lesson 1 Summary

 * 1. What are luminous and illuminated objects?**

__Luminous Objects-__ generate their own light - ex. the Sun

__Illuminated Objects-__ capable of reflecting light to our eyes - ex. the moon - humans are illuminated objects

Without luminous objects generating light that propagates through space to illuminate non-luminous objects, those non-luminous objects cannot bee seen.


 * 2. How do we see objects in a plane mirror?**

__Line of Sight-__ directing of our sight in a specific direction In order to view an object, you must sight along a line at that object; and when you do light will come from that object to your eye along the line of sight.

__Incident Ray-__ the light ray approaching the mirror, intersects the mirror at the same location where your line of sight intersects the mirror

__Reflected Ray-__ ray that reflects off the mirror and travels to your eye



-The object distance always equals the image distance for plane mirrors


 * 3. What is the Law of Reflection?**



__Normal Line-__ perpendicular to the surface of the mirror (N) __Angle of Incidence-__ angle between the incident ray and the normal (theda-i) __Angle of Reflection__- angle between the reflected ray and the normal line (theda-r)

__Law of Reflection__- when a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection


 * 4. What is specular and diffuse reflection?**

__Specular Reflection-__ reflection off of a smooth surface like a mirror or paper

__Diffuse Reflection-__ reflection off of a rough surface like asphalt
 * Still follows the law of reflection, but each ray meets the surface with a different orientation, causing the different rays to scatter in different directions

Reflection Lesson 2 Summary

 * 1. Why is an image formed?**

The image location is located at that position where observers are sighting when viewing the image of an object

When each line of sight is extended backwards, each line will intersect at the same point. This point is the image point of the object.

__Image Location__- the one location in space where it seems to every observer that the light is diverging from - the image location is directly across the mirror from the object location and an equal distance from the mirror

//An image is formed because light emanates from an object in a variety of directions. Some of this light (which we represent by rays) reaches the mirror and reflects off the mirror according to the law of reflection. Each one of these rays of light can be extended backwards behind the mirror where they will all intersect at a point (the image point). Any person who is positioned along the line of one of these reflected rays can sight along the line and view the image - a representation of the object.//


 * 2. What are the characteristics of images in plane mirrors?**

__Virtual Image-__ images that are formed in locations where light does not actually reach - Light does not actually pass through the location on the other side of the mirror; it only appears to an observer as though the light is coming from this location.

Characteristics - located behind the mirror - upright - left-right reversal - object distance = image distance - object size = image size (magnification x1)


 * 3. How do you draw a ray diagram for plane mirrors?**

__Ray Diagram-__ traces the path that light takes in order for a person to view a point on the image of an object

Step 1: Use the principal that object distance is equal to image distance. Pick one extreme of the object and measure its distance from the mirror. Mark off the same distance on the other side. Repeat this for all extremes of the object until the complete location and size is determined.

Step 2: Use the line of sight principal. Draw a bold line for the reflected ray, and a dashed line for the extension of this reflected ray. The arrowhead should point towards the eye.

Step 3: Draw the incidence ray from the extreme of the object to the point of incidence on the mirrors surface. Arrowhead should point towards the mirror.

Step 4: Repeat steps 2 + 3 for all other extremities of the object.


 * 4. What portion of a mirror is required to see an image?**

The man only needs the portion of mirror extending between points X and Y in order to view his entire image

The height of the mirror must be 1/2 the height of the man for him to see his entire image.

Distance from the mirror does **not** affect his relationship.


 * 5. What is a right angle mirror?**



__Primary Image-__light is reflecting off a single mirror before arriving at your eye (Diagram A & B), observes the left-right reversal rule __Secondary Image-__ seen as the result of a double reflection, does not observe the left-right reversal rule (Diagram C)


 * 6. What are other multiple mirror systems?**

One observes that as the angle between the mirrors decreases, the number of images that can be seen increases. In fact as the angle between the mirrors approaches 0 degrees the number of images approaches infinity.

**Reflection Lesson 3 Summary**

 * 1. What is the anatomy of a curved mirror?**

__Concave mirrors-__ were silvered on the inside of the sphere and __Convex mirrors-__ were silvered on the outside of the sphere.

__Principal Axis-__ **l**ine passing through the center of the sphere and attaching to the mirror in the exact center of the mirror __Center of Curvature-__ The point in the center of the sphere from which the mirror was sliced (C) __Vertex-__ The point on the mirror's surface where the principal axis meets the mirror (A) __Focal Point-__ Midway between the vertex and the center of curvature is a point (F) __Radius of Curvature-__ distance from the vertex to the center of curvature (R) __Focal Length-__ the distance from the mirror to the focal point (f)



__Real Images-__ Light actually passes through the image location - concave mirrors produce real images



__Image Location__- the point where multiple reflected rays intersect

**2. What are the laws of reflection for concave mirrors?**

-Any incident ray traveling parallel to the principal axis on th way to the mirror will pass through the focal point upon reflection -Any incident ray passing through the focal point on the way to the mirror will travel parallel to the principal axis upon reflection



**3. How do you draw ray diagrams for concave mirrors?**

Step 1: Pick a point on the top of the object and draw two incident rays traveling towards the mirror. Using a straight edge, accurately draw one ray so that it passes exactly through the focal point on the way to the mirror. Draw the second ray such that it travels exactly parallel to the principal axis. Place arrowheads upon the rays to indicate their direction of travel. Step 2: Once these incident rays strike the mirror, reflect them according to the two rules of reflections or concave mirrors.

The ray that passes through the focal point on the way to the mirror will reflect 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 mirror will reflect and travel through the focal point. Place arrowheads upon the rays to indicate their direction of travel. Extend the rays past their point of intersection.

Step 3: Mark the image of the top of the object.

The image point of the top of the object is the point where the two reflected rays intersect. If your were to draw a third pair of incident and reflected rays, then the third reflected ray would also pass through this point. This is merely the point where all light from the top of the object would intersect upon reflecting off the mirror. Of course, the rest of the object has an image as well and it can be found by applying the same three steps to another chosen point.

Step 4: Repeat the process for the bottom of the object.

The goal of a ray diagram is to determine the location, size, orientation, and type of image that is formed by the concave mirror. Typically, this requires determining where the image of the upper and lower extreme of the object is located and then tracing the entire image. After completing the first three steps, only the image location of the top extreme of the object has been found. Thus, the process must be repeated for the point on the bottom of the object. If the bottom of the object lies upon the principal axis (as it does in this example), then the image of this point will also lie upon the principal axis and be the same distance from the mirror as the image of the top of the object. At this point the entire image can be filled in.

Ray Diagram for the Formation of a Virtual Image

Ray Diagram fo the Formation of a Real Image

**5. What are the image characteristics for concave mirrors?**

The characteristics of concave mirrors vary based on the situation. Case 1: the object is located beyond the center of curvature so the image will be located somewhere in between the C and the F, image is inverted, and reduced in size, real image. Case 2: the object is located at the center of the curvature so the image will also be located at the C, image is inverted, and size is unchanged, real image Case 3: the object is located between the C and F, image will be beyond the C, inverted, larger in size, real image Case 4: the object is located at the focal point so NO IMAGE FOUND! Case 5: the object is located in front of the F, located somewhere on the opposite side of the mirror, upright image, magnified (greater dimensions), virtual image

**6. What is the mirror/magnification equations and sign conventions for concave mirrors?** __ Mirror Equation __

__Magnification Equation__




 * 6. What is spherical aberration?**

__Aberration__ - a departure from the expected or proper course.

This defect prohibits the mirror from focusing all the incident light from the same location on an object to a precise point.

Rays that strike the outer edges of the mirror fail to focus in the same precise location as light rays that strike the inner portions of the mirror.

The two incident rays that strike the outer edges (top and bottom) of the concave mirror fail to pass through the focal point. This is a //departure from the expected or proper course//.



Any incident ray that strikes the outer edges of the mirror is subject to this //departure from the expected or proper course//.

Reflection Lesson 4 Summary

 * 1. How are images formed in convex mirrors?**



Convex mirrors form virtual images, located behind the mirror.

__Virtual Image-__ Light d oes not actually pass through the image location. It only appears to observers as though all the reflected light from each part of the object is diverging from this virtual image location.

__Image Location-__ point of intersection of all extended reflected rays

__Two rules of reflection for convex mirrors:__


 * Any incident ray traveling parallel to __ [|the principal axis] __ on the way to a convex mirror will reflect in such a manner that its extension will pass through the __ [|focal point] __.
 * Any incident ray traveling towards a convex mirror such that its extension passes through the __ [|focal point] __ will reflect and travel parallel to __ [|the principal axis] __.


 * 2. How do you draw ray diagrams for convex mirrors?**

Step 1: draw one ray so that it goes towards the focal point on the opposite side of the mirror to the point of incidence. Draw the second ray parallel to the principal axis.



Step 2: When the rays strike the mirror, reflect them based on the two rules of reflection for convex mirrors



Step 3: Locate and mark the image. The image occurs where the two rays of reflection intersect.



Step 4: Repeat 3 for the bottom of the object If the bottom of the object lies upon the principal axis (as it does in this example), then the image of this point will also lie upon the principal axis and be the same distance from the mirror as the image of the top of the object.


 * 3. What are the image characteristics for convex mirrors?**

IMAGES FROM CONVEX MIRRORS ARE ALWAYS
 * located behind the convex mirror
 * a virtual image
 * an upright image
 * reduced in size (i.e., smaller than the object)


 * 4. What are the mirror/magnification equations for convex mirrors?**

Mirror Equation

Magnification Equation

Color Lesson 1d Summary

 * 1. What is polarization?**

__Unpolarized Light-__ a light wave that is vibrating in more than one plane

__Polarized Light-__ vibrations occur in single planes

__Polarization-__ the process of transforming unpolarized light to polarizing light

__Polaroid Filter-__ made of special material that is capable of blocking one of the two planes of vibration of an electromagnetic wave



__Polarization by Reflection__- polarization when reflected off non-metalic surfaces, dependent upon the angle that light approaches and the material that the surface is made of



__Polarization by Refraction-__ polarization when a beam of light passes from one material to another material, the path of the beam changes its direction and undergoes some polarization when at the surface of the two materials



__Polarization by Scattering-__ polarization when light strikes the atoms of a material many times, and vibrating electrons create their own electromagnetic waves. This causes absorption and reemission of light, which scatters the light and polarizes it as well.

Color Lesson 2 Summary

 * 1. What is the electromagnetic spectrum and the visible light spectrum?**

__Electromagnetic Waves-__ are capable of traveling through a vacuum - produced by a vibrating electric charge - consist of both an electric and magnetic component

__Electromagnetic Spectrum-__ continuous range of frequencies of electromagnetic waves

__Visible Light Spectrum-__ range of wavelengths extends from 7 x 10-7 meter to 4 x 10-7 meter, range that the human eye can see



__Dispersion-__ light shining through a prism will be separated into its different wavelengths, and will thus show the various colors that visible light is comprised of

__White Light-__ white is the combination of all the colors of the visible light spectrum. - If all the wavelengths of the visible light spectrum give the appearance of white, then none of the wavelengths would lead to the appearance of black. - black is merely the absence of the wavelengths of the visible light spectrum


 * 2. How does the eye respond to visible light?**

Light that enters the eye through the pupil ultimately strikes the inside surface of the eye known as the retina.

__Retina-__ lined with a variety of light sensing cells known as rods and cones - rods on the retina are sensitive to the intensity of light - cones are the color-sensing cells (three kinds: red, blue, green)


 * 3. How is light absorbed, transmitted, and reflected?**

Reflection and transmission of light waves occur because the frequencies of the light waves do not match the natural frequencies of vibration of the objects.

__Transmitted-__ vibrations of the electrons are passed on to neighboring atoms through the bulk of the material and reemitted on the opposite side of the object (transparent objects)

__Reflected-__ the electrons of atoms on the material's surface vibrate for short periods of time and then reemit the energy as a reflected light wave (opaque objects)

__Absorbed-__ if an object absorbs all of the frequencies of visible light except for the frequency associated with green light, then the object will appear green

__Pigments-__ chemicals that are capable of selectively absorbing one or more frequency of white light


 * 4. What is color addition?**

__White-__ the presence of all the frequencies of visible light

__Primary Colors of Light-__ Any three colors of light that produce white light when combined with the correct intensity - Red + Green + Blue = White

__Secondary Colors of Light-__ produced by the addition of equal intensities of two primary colors of light (magenta, cyan, and yellow)

__Complementary Colors-__ Any two colors of light that when mixed together in equal intensities produce white - Ex. Red and Cyan, Green and Magenta, Blue and Yellow

__Color Addition-__ production of various colors of light by the mixing of the three primary colors of light


 * 5. What is color subtraction?**

__The Process of Color Subtraction-__ the ultimate color appearance of an object is determined by beginning with a single color or mixture of colors and identifying which color or colors of light are subtracted from the original set



__Pure Pigment-__ absorbs a single frequency

The color of light absorbed by a pigment is merely the complementary color of that pigment.



Refraction Lesson 1 Summary

 * 1. What is refraction and the boundary behavior of a wave?**

__Reflected Pulse-__ A disturbance that returns in the opposite after bouncing of a boundary __Transmitted Pulse-__ A disturbance that continues through the boundary into the new medium

__Refraction-__ the bending of the path of light (is a boundary behavior)


 * 2. How does refraction apply to sight?**

Distortion is an effect of the refraction of light. The eye-brain interaction cannot account for the refraction of light.

Light rays from the submerged portion of the pencil will intersect in a different location than light rays from the portion of the pencil that extends above the surface of the water. For this reason, the submerged portion of the pencil appears to be in a different location than the portion of the pencil that extends above the water.d




 * 3. Why is refraction caused?**

Conditions of Refraction
 * Light must change speed when crossing the boundary.
 * Lights must approach the boundary at an angle; refraction will not occur when it approaches the boundary//head-on// (i.e., heading perpendicular to it).


 * 4. What is optical density and light speed?**

__Optical Density-__ relates to the sluggish tendency of the 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-__ the number of times slower that a light wave would be in that material than it is in a vacuum




 * 5. How do you determine the direction of refraction?**

__Light Traveling From a Fast to Slow Medium-__ 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.

__Light Traveling From a Slow to Fast Medium__- 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.

__Least Time Principal-__ 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.

__FST-__ __**F**__ast to __**S**__low, __**T**__owards Normal

__SFA-__ __**S**__low to __**F**__ast, __**A**__way from Normal

**Refraction Lesson 2 Summary**

 * 1. What is the angle of refraction?**



__Amount of Bending-__ difference between the angle of refraction and the angle of incidence


 * 2. What is Snell's Law?**




 * 3. How do you trace rays and solve problems?**

__Layer Problem-__ the light refracts upon entering the layer, and again upon leaving the layer


 * When light approaches a layer that has the shape of a parallelogram that is bounded on both sides by the same material, then the angle at which the light enters the material is equal to the angle at which light exits the layer.

Refraction Lesson 3 Summary

 * 1. What is total internal reflection?**

__Total Internal Reflection-__ reflection of the total amount of incident light at the boundary between two media

Requirements for Total Internal Reflection
 * the light is in the more dense medium and approaching the less dense medium.
 * the angle of incidence is greater than the so-called critical angle.




 * 2. What is a critical angle?**

__Critical Angle-__ the largest angle of incidence for which refraction can still occur

The critical angle can be calculated by taking the inverse-sine of the ratio of the indices of refraction.

Refraction Lesson 4 Summary

 * 1. What is dispersion?**

__Dispersion-__ The separation of visible light into its different colors (different wavelengths)

__Angle of Deviation-__ the angle made between the incident ray of light entering the //first face// of the prism and the refracted ray that emerges from the //second face// of the prism

- light changes mediums from air to water when it goes through a droplet - the light bends towards the normal - light refracts into the droplet, internally reflects, and then refracts out of the droplet - a collection of suspended droplets in the atmosphere that are capable concentrating the dispersed light at angles of deviation of 40-42 degrees relative to the original path of light from the sun
 * 2. How is a rainbow formed?**




 * 3. What is a mirage?**

__Mirage-__ an optical phenomenon that creates the illusion of water and results from the refraction of light through a non-uniform medium

Refraction Lesson 5 Summary

 * 1. What is the anatomy of a lens?**



__Converging Lens-__ lens that converges rays of light that are traveling parallel to its principal axis

__Diverging Lens-__ lens that diverges rays of light that are traveling parallel to its principal axis

__Double Convex Lens-__ symmetrical across both its horizontal and vertical axis, is a converging lens

__Double Concave Lens-__ symmetrical across both its horizontal and vertical axis, is a diverging lens



__Principal Axis-__ line passing through the center of the sphere and attaching to the mirror in the exact center of the lens

__Vertical Axis-__ bisects the symmetrical lens into halves

__Focal Point-__intersection point, lenses have two focal points

__Focal Length-__ the distance from the mirror to the focal point

__2F Point-__ point on the principal axis that is twice as far from the vertical axis as the focal point is


 * 2. How does refraction occur in lenses?**

__Refraction Rule for a Converging Lens-__
 * 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.
 * An incident ray that passes through the center of the lens will in affect continue in the same direction that it had when it entered the lens.



__R efraction Rule for a Diverging Lens- __
 * 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.
 * An incident ray that passes through the center of the lens will in affect continue in the same direction that it had when it entered the lens.




 * 3. How are images formed by lenses?**

__Converging Lenses__ - produce real and virtual images - images are formed at locations where any observer is sighting as they view the image of the object through the lens



__Diverging Lenses__ - produce only virtual images because refracted rays to not actually converge at a point - image location is located on the object's side of the lens where the refracted rays would intersect if extended backwards




 * 4. How are ray diagrams drawn for converging lenses?**

Step 1: Draw one ray so that it passes through the focal point, draw the second ray so that it travels parallel to the principal axis, draw the third ray so that it travels exactly to the center of the lens.



Step 2: The ray that passes through the focal point will refract and travel parallel to the principal axis. The ray that went parallel to the principal axis will refract and travel through the focal point. The ray that travelled to the exact center of the lens will continue in the same direction.

Step 3: Find the point where the three rays intersect to mark to the top of the image.




 * Real image is formed when the object is behind 2F, at 2F, or between 2F and F.
 * Virtual image is formed when the object is less than one focal length away from the converging lens.


 * 5. What are the characteristics of images in converging lenses?**

Case 1: Object is located beyond 2F - Real - Inverted - Decreased in Size

Case 2: Object is located at 2F (reflects over the principal axis) - Real - Inverted - Same Size

Case 3: The Object is located between 2F and F - Real - Inverted - Larger

Case 4: Object is located at F - no image formed

Case 5: Object is located in front of F - Virtual - Upright - Larger


 * 6. How are ray diagrams drawn for diverging lenses?**

Step 1: The first ray is drawn through the focal point to the lens (but will not actually reach the focal point). The second ray should be drawn parallel to the principal axis. The third ray to the exact center of the lens.



Step 2: The first ray will refract and go parallel to the principal axis. The second ray will refract and go through the focal point. The third ray will travel in the same direction.



Step 3: Extend the lines behind the mirror and find the spot where the three rays converge.




 * 7. What are the object image relationships for diverging lenses?**

Characteristics of All: - Virtual - Behind the Mirror - Upright - Reduced in Size

Refraction Lesson 6 Summary

 * 1. What is the anatomy of the eye?**



__Cornea-__ thin membrane that has an index of refraction of approximately 1.38, has a dual purpose of protecting the eye and refracting light as it enters the eye

__Pupil-__ merely an opening, the light that the pupil allows to enter the eye is absorbed to the retina and does not exit the eye

__Iris-__ colored part of the eye, diaphragm that is capable of stretching and reducing size of the opening

__Crystalline Lens-__ made of layers of a fibrous material that has an index of refraction of 1.4, able to change its sjhape and serves to fine-tune the vision process

__Ciliary Muscles-__ relax and contract in order to change the shape of the lens, assist the eye in the critical task of producing an image on the back of the eyeball

__Retina-__ inner surface of the eyes, contains rods and cones that detect the intensity and frequency of incoming light

__Optic Nerve-__ network of nerve cells bundled together on the very back of the eyeball


 * 2. How are images formed and detected by the eye?**

Most refraction occurs at the cornea. The index of refraction of the cornea is significantly greater than that of the surrounding air. This difference in optical density combine with the fact that the cornea is shaped like a converging lens allows to cornea to do most of the refracting of incoming light. The bulging shape of the cornea causes light to refract in a manner similar to a double convex lens. The cornea-lens system creates an image on the object of the retinal surface. The image is real.




 * 3. What is accommodation?**

__Fovea Centralis-__ the optimal location for the formation of the image

__Accommodation-__ the ability of the eye to adjust its focal length



__Diopters-__ the reciprocal of the focal length

__Power of Accommodation-__ the maximum variation in the power of the eye


 * 4. How is farsightedness corrected?**

__Farsightedness/Hyperopia-__ the inability of the eye to focus on nearby objects - must assist the lens in in refracting the light, the lens can no longer assume the convex and highly curved shape that is required to view nearby objects - converging lens will refract light before it enters the eye and decrease the image distance


 * 5. How is nearsightedness corrected?**

__Nearsightedness/Myopia-__ inability to focus on distant objects - equip the eye with a diverging lens - the light is focused in front of the retina, so a diverging lens will serve to diverge light before it reaches the eye - light will then be converged by the cornea and lens to produce an image on the retina