Physics midterm problem: out-of-phase source interference

Physics 205B Midterm 1, spring semester 2011
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problems 25.1, 25.3

[20 points.] A radio transmitter sends a signal of wavelength 0.18 km to a receiver 1.22 km away. 
The signal also travels to the receiver by another path where it reflects with a 180° phase shift from a metal skyscraper, as shown at right. As a result, there is a destructive signal at the receiver. Find the shortest possible distance between the skyscraper and the receiver. Show your work and explain your reasoning.

Solution and grading rubric:

• p = 20/20:
  Correct. Sets up proper destructive interference condition for out-of-phase sources (∆l = m·λ), where ∆l = (1.30 km - x) - 1.22 km, and solves for x, the distance from the skyscraper to the receiver using m = 1 to obtain the shortest possible skyscraper-receiver distance.
  
• r = 16/20:
  Nearly correct, but includes minor math errors.
  
• t = 12/20:
  Nearly correct, but approach has conceptual errors, and/or major/compounded math errors.
  
• v = 8/20:
  Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner.
  
• x = 4/20:
  Implementation of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30882
Exam code: midterm01g74S
p: 2 students
r: 0 students
t: 4 students
v: 0 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 2414):

Physics midterm problem: bifocal prescription

Physics 205B Midterm 1, spring semester 2011
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 24.24

"Image of an eyeglass prescription"
Dpbsmith

http://en.wikipedia.org/wiki/File:Specrx-prescription2.jpg

Shown above is an (edited) copy of an eyeglass prescription, where the far and near corrective optics are prescribed to be –3.25 diopters and +2.00 diopters, respectively, for the right and left eyes. Determine (a) the uncorrected far point for the right eye, and (b) the uncorrected near point for the left eye of this patient. (Neglect the distance between these glasses and eyes.) Show your and explain your reasoning using properties of lenses and vision.

Solution and grading rubric:

• p:
  Correct. Uses the thin lens equation 1/p + 1/q = 1/f = P, where p is the far point F or near point N, and q = –∞ or –0.25 m, respectively, and solves for F and N. Minor negative sign errors okay.
  
• r:
  Nearly correct, but includes minor math errors.
  
• t:
  Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. Applies F = –1/D correctly to find far point, but incorrectly applies N = 1/P to find near point; or may use N = 1/(P – 1/(0.25 m)) correctly to find near point, but incorrectly applies it to find the far point.
  
• v:
  Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner.
  
• x:
  Implementation of ideas, but credit given for effort rather than merit.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distribution:
Section 30882
Exam code: midterm01g74S
p: 1 student
r: 0 students
t: 7 students
v: 0 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 2180) with a relatively minor sign error:

Overheard: Horsehead Nebula dementor

Astronomy 210, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

The_Horshead_Nebula [sic]
http://commons.wikimedia.org/wiki/File:The_Horshead_Nebula.jpg
Originally uploaded by the European Southern Observatory

(Overheard during slide presentation on emission/reflection/dark nebulae, with slide of Barnard 33 (Horsehead Nebula) on-screen.)

Instructor: "Just like when you look at clouds overhead, astronomers love to look at nebulae in space, and ask themselves, 'Okay, what does that look like?'" (Turning around and gesturing towards slide of Barnard 33) "So, what does this nebula look like to you?"

(Beat.)

Student: "Like a dementor--from Harry Potter!"

Astronomy quiz archive: sun/spectra/star properties

Astronomy 210 Quiz 4, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

Section 30674, version 1
Exam code: quiz04nK4n

Section 30674

Quiz 4 results (max score = 40):
   0- 8.0 : *  [low = 2.5]
 8.5-16.0 : ******
16.5-24.0 : *************  [mean = 23.1 +/- 7.3]
24.5-32.0 : *************
32.5-40.0 : ****  [high = 40.0]

Section 30676, version 1
Exam code: quiz04s0sO

Section 30676

Quiz 4 results (max score = 40):
   0- 8.0 : *  [low = 5.0]
 8.5-16.0 : ***********
16.5-24.0 : ****************  [mean = 20.5 +/- 7.8]
24.5-32.0 : ******
32.5-40.0 : *******  [high = 40.0]

Astronomy in-class activity: OBAFGKM poetry slam (SLO)

stronomy 210, Spring Semester 2011
Cuesta College, San Luis Obispo, CA
(San Luis Obispo Campus)

Astronomy 210 In-class activity 14: OBAFGKM Poetry Slam

Students were instructed to use at least OBAFGKM, and/or part or all of the additional OBAFGKMRNSC or OBAFGKMLT extensions to individually write an original, coherent and an appropriate (nothing worse than "PG-13" rated!) mnemonic, and to give a rousing reading of their OBAFGKM mnemonic poem for the class.

Only Boys At Fairs Get Kicked Making Lame Taunts
--D. A.
Oh Boy, A Fat Girl Kicked My Left Testicle
--M. B.

Onion-Breather Astronomers Frighten Good, Kind Mr. Len
--D. B.

Only Badass Astronomers Freakin Go Kayaking Man
--M. C.

Oh Baby A Ford Galaxy Killed Me
--R. D.

Orange Bears Always Fight Gay Klan Members
--M. D.

Only Belle Abhors Feisty Gaston's Kind Marriage Requests
--J. H.-D

Only Ballin' Aliens Fly Gnarly Keyless Machines
--J. D.

Overcoming Basic Astronomy Final Gonna Kill Me
--J. G.

Ostrich Babies Assemble For Gambling Kangaroo Muds
--P. G.

Only Bieber Allows Frantic Girls' Kisses on Mondays
--N. H.

Oh Boy Another Friday night Gave Killer Munchies
--S. H.

Off Brand Aftermarket Footwear Gets Kinda Messed Up Some Times
--D. A. J.

Optative Birthdays Are Full (of) Gallivanting. Keep (the) Memories. Love (the) Times.
--H. J.

Oh Behave About Frolicking Gorillas Kicking Marky Mark
--C. J.

Oh Be A Friend, Give Kisses More!
--L. L.

Otters Bask Among Fresh Gardens of Kelp Masses
--H. M.

Oh Boy All Family Get-togethers Kill Me
--D. M.

Our Brother Attacked Flying Growing Killer Monkeys
--J. M.

Only Brilliant Astronomers Find Great Killer Meteors
--An. M.

Ostrich Balls Are From Gross Korean Meals (we ate) Last Time
--Au. M.

Only Bill Always Felt Guilty Kissing Monkeys
--D. M.

Outraged Bear Attacks Family of Gangsta Koala Murdering
--Z. N.

Once By A Famous Giant Kasino My Rude Nephew Shouted Curse words
--E. O.

Only Baseball And Football Get Killer Money
--E. P.

Over-eating Brothers Always Finish Good Korean Meals
--K. P.

Orbiting Ballistic Aircraft Furiously Giving Kinetic Motion!
--E. R.

Orion's Belt Always Fits Good with Kepler's Model
--J. R.

Oh Baby Almost Freakin Gonna Kry Myself to sleep
--T. R.

Obviously Bears Always Forget Good Kind Manners
--B. S.

Only Brats Are Foolish Girls Killing Men
--S. S.

On Boring Afternoons Fun Games My Life Thrilling
--E. S.

Only Baseballs A Favorites Get Killer Money
--G. S.

Obama Bought A Freakin Giant to Kill Men Like the Taliban
--M. T.

Old Birds Are Forever Going Koo-koo in My Little Tree
--S. T.
Obama Bakes Apple pie For Ghetto Kids' Moms
--A. U.

Obama Bashes Americans For Getting Korean Mangoes
--A. V.
Oranges Beats Apples From Giving Killer Mangos
--S. V.

Our Brother Admits Forgetting Good Karma Man!!!
--S. W.


Previous post:

• Astronomy in-class activity: OBAFGKM poetry slam instructions.

Astronomy in-class activity: OBAFGKM poetry slam (NCC)

Astronomy 210, Spring Semester 2011
Cuesta College, San Luis Obispo, CA
(North County Campus)

Astronomy 210 In-class activity 14: OBAFGKM Poetry Slam

Students were instructed to use at least OBAFGKM, and/or part or all of the additional OBAFGKMRNSC or OBAFGKMLT extensions to individually write an original, coherent and an appropriate (nothing worse than "PG-13" rated!) mnemonic, and to give a rousing reading of their OBAFGKM mnemonic poem for the class.

Only Brilliant Astronomers Freaken Give Kim Millions
--Y. A.

Our Butts And Feet Got Kinks Man
--C. A.

Our Beautiful Apples Fell, Grossly Killing Martha
--As. B.

Oatmeal Breakfasts Are Fine, Grumpy Kids Make Random Noises to Stop Chewing
--Am. B.

Objects Be Apparent From Galaxies, Knew M______
--M. B.

Octopus Babies Are From Gnome Killing Mobs
--J. B.

Oswald Bounds Away from Grumpy Koala Mafia
--B. B.

Our Brave Army Fight Germs Killing Military Rebels Never Sound Cultures Love Them
--E. B.

On Back And Front Gaining Knowledge Makes Real Nice Sense Concentrate
--T. B.

Obviously Bats Are Filling Good at Keeping Monkeys
--M. C.

Old Bears, Away From Good Kind Moose, Run Near Secluded Clearings
--C. D.

Only Bowser Attacks Famous Great King Mario
--C. E.

Oh Baby A Freak Gonna Kill Me
--D. F.

Obama, Barack Always Farts (while) Giving Kisses (to) Michelle
--K. F.

Old Babies Ask For Gerber, Kraft Mac & Cheese
--X. G.

Only Bad Ass Felines Growl (at) Kitchen Machines
--E. H.

Observe Bombing Air-raids For Giant Killing Machines
--K. H.

Old Baboons Are Fairly Good Kool-Aid Makers Respectfully, Not Smelly Chimpanzees
--L. H.

Only Brilliant And Focused Guys Kiss Moms
--B. H.

Obama Bet Adam Five Grenade Kaboom Muffins
--T. H.

Only Bad Ass Friends Give Kailey Money
--K. L.

Old Bachelors And Friends Go Kipping Mondays
--A. L.

Once Befriended A F*****, Guy Knew my Mother
--T. L.

Obnoxious Betelgeuse Acquires Foreign Gangster's Kite Money
--J. L.

Only Batman And Flash Go Kick Manray
--D. N.

Only Babies Are Fed Grape Kittle Munchies
--R. O.

Oh Blue Astronomically Far Giant Kepler Moon
--D. P.

Oh Baby Aren't Flowers Gorgeous, Kevin Marry me!
--E. S.

Omar Bradley's Aunt, and Father Got Kind of Mad
--D. S.

Oh Be A Fine Guy Kiss Me!
--S. S.

Orbital Ballistic Autonomously Flight Guided Kinetic Missile
--B. T.

Only Butterflies Attack Flying Gorillas Killing Many
--H. T.
Oh, Bieber's A Faker, Gonna Kill Music
--M. T.

Orangutan Babies Are Funny Game Knowing Monkeys
--E. V.

Oprah Better Apologize For Googling the Kardashians' Men
--A. V.

Outta Beer And Feeling Great, Kiss Me!
--K. W.

Previous post:

• Astronomy in-class activity: OBAFGKM poetry slam instructions.

Cuesta College North County campus star party

110310-1220606
http://www.flickr.com/photos/waiferx/5527513646/
Originally uploaded by Waifer X

Waxing crescent moon, March 10, 2011, photographed with a Panasonic Lumix LZ-8 camera through a Orion 10" reflector at Cuesta College North County campus, Paso Robles, CA. Photo by Cuesta College Physical Sciences Division instructor Dr. Patrick M. Len.

110310-1220611
http://www.flickr.com/photos/waiferx/5527514072/
Originally uploaded by Waifer X

Cuesta College Astronomy 210L students and guest (and a cold dog) at a North County campus star party.

Sights seen:
M42 (Orion nebula)
Castor, Pollux
Sirius
Waxing crescent moon

Physics quiz archive: interference, electrostatics

Physics 205B Quiz 3, spring semester 2011
Cuesta College, San Luis Obispo, CA

Section 30882, version 1


Section 30882 results
Exam code: quiz03F3ld

 0- 6 : 
 7-12 : 
13-18 : ****  [low = 18]
19-24 : ***  [mean = 19.7 +/- 2.4]  [high = 24]
25-30 :  

Astronomy midterm question: waning crescent scenario

Astronomy 210 Midterm 1, spring semester 2011
Cuesta College, San Luis Obispo, CA

Shown at right is a scene from an animated TV show. Discuss a specific plausible time (or range of times) for this scene, assuming that it is not an eclipse, using a diagram showing the positions of the sun, moon, Earth, and an observer on Earth.

(Image credit: Matt Groening, Futurama, "Rebirth," Season 6, Episode 1, 20th Century Fox Television, 2010, 
http://www.gotfuturama.com/Multimedia/FrameGrabs/6ACV01/.)

Solution and grading rubric:

• p = 20/20:
  Correct. Phase as shown is waning crescent, which is highest overhead at 9 AM (rises at 3 AM, and sets at 3 PM, so any time within that range would be plausible, may restrict times to between 3 AM to 6 PM as the sky is still dark, and moon is not yet fully upright/on the meridian). Correct diagram and reasoning.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram, phase, or time.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Problems with diagram, phase, and time.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Explanation based on eclipses, solstices, etc.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30676
Exam code: midterm01sl7k
p: 22 students
r: 4 students
t: 8 students
v: 13 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 4351):

Astronomy midterm question: late-night Venus, Jupiter?

Astronomy 210 Midterm 1, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

[20 points.] An astronomy question on an online discussion board was asked and answered:

mickafeld: ...How do you [tell] the difference between Venus and Jupiter?
duke_of_uris: If you see a very bright planet late at night, it's Jupiter [and not Venus]...
-- http://au.answers.yahoo.com/question/index?qid=20100507202644AANiYYU

Discuss if this answer is correct or incorrect, and how you know this. Support your answer using a diagram showing the positions of the sun, Venus, Jupiter, Earth, and an observer on Earth.

Solution and grading rubric:

• p = 20/20:
  Correct. Correct and complete diagram, with Venus (inner heliocentric orbit) and Jupiter (outer heliocentric orbit); Jupiter can be seen late at night if it is near opposition to Earth, but Venus cannot in any part of its orbit.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Typically has diagram of heliocentric orbits of Venus, Earth, and Jupiter, but discussion is problematic.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Diagram is problematic (Venus and Jupiter both in inner heliocentric orbits, or both in outer heliocentric orbits), but at least discussion is consistent with incorrect diagram.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Problematic diagram (geocentric orbits, no orbits etc.), problematic discussion.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30676
Exam code: midterm01sl7k
p: 18 students
r: 7 students
t: 5 students
v: 6 students
x: 12 students
y: 1 student
z: 0 students

A sample "p" response (from student 1103):

Astronomy midterm question: telescope comparison

Astronomy 210 Midterm 1, spring semester 2011
Cuesta College, San Luis Obispo, CA

[20 points.] An astronomy question on an online discussion board was asked and answered:

Emma B: Which one of these telescopes [is] the better telescope?


Celestron™ 21061 AstroMaster® 70 AZ Refractor
      [70 mm diameter lens, 900 mm long tube, f = 20 mm eyepiece]

Orion™ SpaceProbe® 3 Altazimuth Reflector

      [76 mm diameter mirror, 700 mm long tube, f = 25 mm eyepiece]
George N: The second one...
--Adapted from http://answers.yahoo.com/question/index?qid=20101214213555AA1VrSt

Discuss whether you agree or disagree with this answer, and the criteria used in your decision. Support your answer using the properties of telescopes and telescope powers.

Solution and grading rubric:

• p = 20/20:
  Correct. Discusses how diameter of primary lens/mirror determines the light-gathering power and resolving power, while the (focal) length determines the magnifying power, the latter of which is the least important due to priority given to collecting light that will result in bright, resolvable images worth magnifying. Thus the Orion(TM) telescope will have better light-gathering power and resolving power, while having less magnifying power, as purchased, but another eyepiece could be used to give it greater magnifying power. Argument may point out nearly comparable LGP and RP (within 8%), while magnification is 60% greater for Celestron(TM) telescope.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Two of three telescope powers discussed correctly, third is problematic/missing.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Only one telescope power discussed correctly, other two problematic.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Only one telescope power discussed correctly with other two missing, or all three problematic.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Primarily makes a decision without substantive discussion of relevant telescope powers.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30674
Exam code: midterm01n0M3
p: 10 students
r: 12 students
t: 7 students
v: 8 students
x: 3 students
y: 1 student
z: 0 students

Grading distribution:
Section 30676
Exam code: midterm01sl7k
p: 19 students
r: 10 students
t: 5 students
v: 10 students
x: 5 students
y: 0 students
z: 0 students

A sample "p" response (from student 0523):

A sample "p" response (from student 1994), disagreeing with George N.'s decision:

Astronomy midterm question: Venus-Jupiter transit

Astronomy 210 Midterm 1, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

[20 points.] Consider an online definition of a type of an eclipse called a transit:

A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body... In rare cases, one planet can transit in front of another.
--http://en.wikipedia.org/wiki/Astronomical_transit

The next planetary transit will occur on November 22, 2065, when Venus transits (passes in front of) Jupiter. Show how this event would be possible, using a diagram showing the positions of the sun, Venus, Jupiter, Earth, and an observer on Earth.

Solution and grading rubric:

• p = 20/20:
  Correct. Correct and complete diagram, with Venus (inner heliocentric orbit) and Jupiter (outer heliocentric orbit) along line of sight of observer on Earth.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. No actual transit in a plausible diagram where Venus (inner heliocentric orbit) and Jupiter (outer heliocentric orbit) are in opposition/conjunction with respect to each other, while Earth may or may not be between Venus and Jupiter. Or draws a transit in a problematic diagram, with both Venus and Jupiter in inner heliocentric orbits, or both in outer heliocentric orbits, where all three planets are in line with the sun.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Draws a transit, but in a geocentric model.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. No transit, problematic model.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30674
Exam code: midterm01n0M3
p: 9 students
r: 1 student
t: 20 students
v: 2 students
x: 7 students
y: 2 students
z: 0 students

A sample "p" response (from student 1450):

A sample "t" response (from student 7624), with Venus orbiting the sun outside Earth's orbit in order to transit Jupiter:

Another sample "t" response (from student 2336), with correct orbits, but no transit as seen from Earth:

A sample "v" response (from student 5259), with Jupiter orbiting Earth closer than Venus in a geocentric model:

Astronomy midterm question: moonset at sunrise?

Astronomy 210 Midterm 1, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

[20 points.] An astronomy question on an online discussion board was asked and answered:

TheworldisRound...: When does the moon set?
Jon: When the sun rises.
--Adapted from http://answers.yahoo.com/question/index?qid=20101117173704AA9FK13

Discuss for which moon phase(s) this answer would be correct, or if this answer would never be correct for any moon phase, and how you know this. Support your answer using a diagram showing the positions of the sun, moon, Earth, and an observer on Earth.

Solution and grading rubric:

• p = 20/20:
  Correct. Moon setting at sunrise (6 AM) would have been highest overhead at 12 AM that same night, which would make it a full moon. Correct diagram and reasoning.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram, phase, or time.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Problems with diagram, phase, and time.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Explanation based on eclipses, solstices, etc.
  y = 2/20: Irrelevant discussion/effectively blank.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30674
Exam code: midterm01n0M3
p: 18 students
r: 3 students
t: 8 students
v: 9 students
x: 3 students
y: 0 students
z: 0 students

A sample "p" response (from student 0920):

Student scribble: "Observing P-Dog"

110304-1220474
http://www.flickr.com/photos/waiferx/5503505281/
Originally uploaded by Waifer X

Student observation logbook, Astronomy 210L, Cuesta College, San Luis Obispo, CA. Photo taken by Cuesta College Physical Sciences Instructor Dr. Patrick M. Len.

Astronomy quiz archive: telescopes

Astronomy 210 Quiz 3, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

Section 30674, version 1
Exam code: quiz03n7uu

Section 30674

Quiz 3 results (max score = 40):
   0- 8.0 : **  [low = 4.0]
 8.5-16.0 : ***********
16.5-24.0 : **********  [mean = 22.6 +/- 8.8]
24.5-32.0 : **********
32.5-40.0 : *********  [high = 36.5]

Section 30676, version 1
Exam code: quiz03s3ts

Section 30676

Quiz 3 results (max score = 40):
   0- 8.0 : *  [low = 6.0]
 8.5-16.0 : ********
16.5-24.0 : *****************  [mean = 23.1 +/- 8.2]
24.5-32.0 : ************
32.5-40.0 : ********  [high = 36.5]

Overheard: floaters and filler-ins

Astronomy 210, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

(Overheard as students are moving to their assigned groups to work on an in-class activity ("lecture-tutorial").)

Student: "What does it mean if the seating chart says I'm a floater/filler-in?"

Instructor: "Just hang back until all the groups are seated. Then look for the smallest, most pathetic-looking group, and then join them for today."

(Beat.)

Instructor: "But don't tell them I told you this."

Overheard: (lack of) assigned seating

Astronomy 210, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

(Overheard at the start of a class without the usual in-class activity ("lecture-tutorial") and requisite assigned seating chart.

Student: "Why is there no seating chart for today?"

Instructor: "Because today you get to find out who your real friends are."

(Beat.)

Instructor: "Or at least find out who loves to sit in your row just as much as you do."

Overheard: texting in class

Astronomy 210, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

(Overheard near the end of an in-class activity ("lecture-tutorial") on the Stefan-Boltzmann law and the Hertzsprung-Russell diagram.)

Student: "Dr. Len? Could you give us some help over here?"

Instructor: (Sighs while texting on phone.) "NOT NOW--CAN'T YOU SEE I'M TEXTING?"