Download Chapter 15: Refraction and Lenses

Chapter 15: Refraction and Lenses
Lecture Questions:
1) What is refraction and when does it occur? When a wave is refracted what
happens to its frequency, wavelength and speed? Which way will a ray bend
when going from a fast to a slow medium? How about when going from a slow
to fast medium? Write Snell’s law and define each of the variables. Define the
index of refraction. Write Snell’s law using the index of refraction.
2) How does the speed of sound vary with the density and temperature of a medium?
How does the speed of light vary with the density and temperature of a medium?
3) Draw a picture showing how we can still receive light from the Sun even after it
sets over the horizon. Explain the formation of the pumpkin sun phenomenon.
4) Draw a picture showing how light is bent in a light mirage. Indicate the areas of
high and low temperature.
5) Draw a picture showing a sound mirage. Again show the areas of high and low
temperature air.
6) What two variables determine the fate of a wave when it hits a boundary? Under
what conditions is a wave absorbed? Under what conditions is a wave reflected
and refracted? Under what conditions is a wave reflected only?
7) Define the critical angle of a substance? What is the refracted angle when the
incident angle equals the critical angle?
8) A Native American sees a fish in the water. In order to spear the fish where
should he aim? What does the fish see when it looks up towards the surface of
the water?
9) Define total internal reflection (TIR). Do objects that experience TIR have large
or small critical angles? Give some examples of TIR.
10) What is dispersion and when does it occur? Draw a picture explaining how a
Moon halo forms. Draw a picture showing how a rainbow forms and where you
need to stand to see one. How does a secondary rainbow form and how is it
different than a primary bow? Why are rainbows, bow shaped?
11) What is the shape of a convex lens and what does it cause parallel light rays to
do? What is the shape of a concave lens and what does it cause parallel light rays
to do?
12) Define the terms center of curvature, principal axis, focal point object and image
for a lens. Which side of a lens is considered the positive side and which the
negative side. Write the distance and magnification equations for a lens.
13) What are the principal rays for a converging lens? Draw ray diagrams for objects
that are: a) within one focal length of the lens b) between one and two focal
lengths of the lens; c) more than two focal lengths from the lens. State what type
of image is formed in each case.
14) What are the principal rays for a diverging lens? Draw a ray diagrams for a
diverging lens. What type of image does a diverging lens form?
15) What are chromatic and spherical aberrations of a lens? What are some solutions
to these problems?
16) What type of lens is used in a camera? Compare the light rays a camera receives
from a near and far object? How is a camera able to focus on near and far objects?
How is the diaphragm of the camera used to focus on near and far objects?
17) What type of lenses is used for a microscope and how are they placed? What type
of lenses is used for a refracting telescope and how are they placed? What type of
image does each of these instruments produce? How do the lenses for a
microscope and telescope differ? What modification is made to these instruments
to allow photography?
18) To what optical instrument is the human eye the closest in function? What is
wrong with the vision of someone who is near sighted, what is the anatomical
cause of this problem and what type of lens is used to correct it? What is wrong
with the vision of someone who is near sighted, what is the anatomical cause of
this problem and what type of lens is used to correct it? What is wrong with the
vision of someone who is far sighted, what is the anatomical cause of this
problem and what type of lens is used to correct it? What is astigmatism and how
is it corrected?
Problems:
1) Find the angle of refraction for a ray of light that enters a bucket of water from air
at an angle of 25.0 degrees to the normal. The indices of refraction for water and
air are 1.333 and 1.000 respectively.
2) A ray of light of vacuum wavelength 550 nm traveling in air enters a slab of
transparent material. The incoming ray makes an angle of 40.0 degrees with the
normal, and the refracted ray makes an angle of 26.0 degrees with the normal.
Find the index of refraction for the transparent material assuming the index of
refraction for air is 1.00.
3) For an incoming ray of light of vacuum wavelength 589 nm, fill in the unknown
values for the following table.
From (medium)
To (medium)
I
r
Flint glass
Crown glass
25.0 degrees
(n=1.66)
(n=1.52)
Air (n=1.00)
14.5 degrees
9.80 degrees
Air (n=1.00)
Diamond
12.5 degrees
(n=2.419)
4) Find the critical angle for light traveling from glycerine (n=1.473) into air.
5) Calculate the critical angle for light traveling from glycerine into water.
6) Find the critical angle for light traveling from ice (n=1.309) into air.
7) Which has a smaller critical angle in air, diamond (n=2.419) or cubic zirconia
(n=2.20)? Show your work.
8) An object is placed 20.0 cm in front of a converging lens of focal length 10.0 cm.
Find the image distance and describe the image.
9) Sherlock Holmes examines a clue by holding his magnifying glass (with a focal
length of 15.0 cm) 10.0 cm away from an object. Find the image distance and
describe the image formed.
10) An object placed 20.0 cm in front of a diverging lens of focal length 10.0 cm.
Find the image distance and describe the image.
11) Fill in the missing values for the following table.
F
P
Q
Converging Lens
6.0 cm
Diverging lens
-6.0 cm
Schedule:
Day
Monday
Tuesday
Wednesday
Thursday
Friday
Monday
Tuesday
Wednesday
Thursday
Friday
2.0 cm
5.0 cm
M
7.0 cm
4.0 cm
5.0 cm
Class Assignment
Lecture: Refraction (Q 1-5)
Lecture: Critical Angle and Dispersion
(Q 6-10)
Problem Solving (P 1-7)
Homework Review and NTQ
Lab: Lens Stations
Lecture: Lenses (Q 11-15)
Lecture: Optical Phenomena (Q 16-18)
Problem Solving (P 8-11)
Homework Review and NTQ
Chapter 15 Quiz
0.50
Homework Due
None
None
None
Chp. 15 Qs 1-16, 37-51
None
None
None
None
Chp. 15 Qs. 17-36
Notebook