20 Physical Science Property of Waves Notes 5
Chapter 15 & 16
A. Refraction
Refraction - the change in the direction of a ray of light when the light goes from one medium to another at an angle
Terms Refracted ray, angle of refraction
What causes refraction?
Do all transparent materials refract light to the same extent?
Lesson Light travels at different speeds in different materials? We use a ratio called “index of refraction” to describe the speed of light through a medium. The index of refraction (n) of a specific substance is the ratio of the speed of light in a vacuum (3.00 x 108) to the speed of light in that substance
see table p. 422 (note: different colours travel at different speeds)
Activity Shine rays from ray box through a prism.
very informal - discussion - what did they observe?
Practice p. 423 # 1-4
p. 440 #15 - 20
Activity Investigation 15.1 p. 434
must know what sine is
replace the word glass with water (save one)
significant figures for each column
find average of last column in the data table
answer questions 1 - 6 (#3 interpret the question for them)
Lesson What was the purpose of the previous activity?
How & why is it that we averaged the last column of the data table?
How did the ratio of sin i to sin r for water compare to that of glass?
Compare the values of these ratios to the respective indices of refraction. Link?
This should lead in to snell’s law.
Snell’s Law & example
Practice p. 424 # 1-3
p. 426 # 1-3
p. 441 # 21- 25, 27 - 31, 35
Applications read p. 430 - 432
position of the sun, shape of the sun, mirages, cedar wood oil
Lesson TIR notes (OHT)
critical angle - snell’s law
Practice p. 428 # 1-3
p. 442 # 32 - 34
Activity Investigation 15.2 p. 435
Questions 1-10
Applications demo laser through plexi-coil (also see p., 428) & light wire (fibre optics)
Fibrescope p. 428
Read p. 433
diamonds p. 434
Practice p. 438 #1, 3 - 12
B. Lenses
Demo two types of lens
virtual and real image possibilities. Obviously the geometry seems to effect the path that light follows and thus the image characteristics.
Activity shine rays from the ray box through two types of two dimensional lenses and determine the effect each has on light.
informal - discussion? - logical names for each type of lens and link to their respective three dimensional counterparts.
Define Converging, diverging, focal points, focal length, geometric centre, principle axis
Make clear the relative positions of objects and principle focus
Ray Diagrams rationale
steps (on OHT from part I)
rules for (on OHT)
practice 5 converging scenarios & 1 diverging scenario
Practice p. 466 # 14 - 15
Activity Investigation 16-1 p.462
must review image characteristics
must know how to find the focal length
must know where to measure distance from
complete data table and questions # 1-6
for Q#6 average values in second last column & stress how to compare numbers and why
Lesson What was the purpose of the previous activity?
How & why is it that we averaged the second last column of the data table?
Conclusion/Link? This should lead in to lens Equation
(review sign convention)
Example #1 - An object 8.0 cm tall is placed 37.0 cm from a converging lens with a focal length of 23 cm. How far away is the image formed, how large is it, what is the magnification and what are the characteristics of the images?
Example #2 - The size of an image is one third that of the object when placed in front of a diverging lens with a focal length of -22.0 cm. How far away is the object from this lens?
Practice p. 453 # 1b, 2b,3,4 &5
p. 467 # 16 - 21 (use the lens equation even though the question reads Use a ray diagram)
p. 467 # 23 - 30
Illustration Chromatic Aberration
Applications The Eye (parts)
ray diagram for normal vision
Myopia - symptoms, cause and correction
Metropia - symptoms, cause and correction
Reading - “ Cataracts” p. 459 - discussion
Astigmatism
Diopters
Applications Demo refracting telescope (need concurrent activity - see below)
ray diagram for telescopes and microscopes
Practice p. 466 # 3 - 5, 8 - 10, & 13