announcements 11/9/11
DESCRIPTION
Announcements 11/9/11. Prayer Term project progress report due Saturday night Evidence of progress Text in body of email, who is in your group, CC group members Slinkies! (Thomas, Mike, Rachael, this means you). Frank & Ernest (with apologies to Pluto). Thought question. - PowerPoint PPT PresentationTRANSCRIPT
Announcements 11/9/11 Prayer Term project progress report due Saturday
nighta. Evidence of progressb. Text in body of email, who is in your group,
CC group members Slinkies! (Thomas, Mike, Rachael, this means
you)
Frank & Ernest (with apologies
to Pluto)
Thought question Which will look bigger* to you, a 1 m tall
object that’s 5 meters away from you, or a 10 m tall image that’s 50 meters away from you?
a. 1 m tall objectb. 10 m tall imagec. same
* In the sense that it takes up more of your field of view
“angular size”
Worked Problem What is the angular size of a 0.1 m tall
object that’s 5 meters away from you?
Two methods!
Thought Question Which method should you use?
a. Method Ab. Method B
Quick writing
You are looking at an ant, h = 1 mm. What is the maximum viewing angle you can use to look at the ant, without any lenses?
r
“Colton picture”
(in radians) = (section of arc)/r
Reading Quiz Which of the following is NOT true of angular
magnification?a. It is more useful than the absolute magnification
when discussing telescopesb. It is more useful than the abs. magnification when
discussing magnifying glassesc. It is given by the equation m = -q/pd. It is likely to show up on an exam.
m = /0 … where 0 = “the best you can do without magnification”
Magnifying Glass The setup:
f = 10 cm
Where would you like the image to be? Let’s pick q = -50 cm. (q would generally be given
in problem.) What is m? (m = /0)
a. What is ?b. What is 0?
Answers: = 6h/50 rad 0 = h/25 radm = 3
Note: using formulas from book…mmax = 3.5 (for q = 25 cm)mmin = 2.5 (for q = infinity)
Aside: What will the ant see?
8.33 cm
h
p
f = 10 cm
If p = 1 cm: q = (1/10 – 1/1)-1 = -1.11
M = -q/p = 1.11
m = /0 = 1.11 9.44
1.109.33
h
h
If p = 9.5 cm: q = (1/10 – 1/9.5)-1 = -190
M = -q/p = 190/9.5 = 20
m = /0 = 20 (190 8.33)
1.80(9.5 8.33)
h
h
If p = 20 cm: q =+20
(ant can’t see you!)
(fixed from in-class values)
Quick writing
You are looking at the planet Mars, “h” (diameter, really) = 3.4 106 m. The planet, as you are looking at it, is 2.5 1011 m away (this changes from month to month based on the relative positions of Mars and Earth). What is the maximum viewing angle you can use to look at Mars, without any lenses?
r
“Colton picture”
(in radians) = (section of arc)/r
Telescope
The setup:
Given details of setup, what is m? (m = /0)
a. What is 0?
b. What is ?
These focal spots should essentially overlap (not shown properly in this figure)
“Colton picture” for
Because Mars is so far away, image is formed at the focal spot (essentially)
fo
Height of image = hfo/r (from M = -q/p)
r
fe
image
If intermediate image were formed exactly at the focal point of the eyepiece, final image would be at . As it is, it will just be very far away.
Regardless of how far away it is, though, the angle is given by the blue ray.
triangle: (rad) = (intermed. height)/fe
Answers:0 = h/r = foh/(rfe)m = fo/fe
Reflecting Telescope
A “Newtonian Reflector”
http://lcogt.net/en/book/reflecting-telescopes
Incoming Light
Mirror
CurvedMirror
eyepiece lens
Compound Microscope
http://en.wikipedia.org/wiki/Microscope
I really dislike the eqn: “overall magnification” =
Mobjective meyepiece
because it mixes absolute magnification with angular magnification
(but apparently everyone does it that way)
Not on reading assignment, not on HW, not on exam, not especially interesting… let’s not bother with. Onward!
Chapter 37!
Interference effectsa. I.e. now returning to wave nature of
light, instead of the ray approximation
Two mathematical facts we will use:
cos2
ix ixe ex
sin
2
ix ixe ex
i
Interference... Interference...
A single source
Next few slides: credit Dr. Durfee
Interference... Interference...
Two sources