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December 14, 2019, 10:49:07 am

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melodrama

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Exam 2 Answer Thread
« on: November 14, 2007, 12:34:57 pm »
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Post answers here. I wrote them on my formula sheet but the ladies TOOK IT AWAY. :(:(:(

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melodrama

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Exam 2 Answer Thread
« Reply #1 on: November 14, 2007, 12:39:36 pm »
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off the top of my head, i remember:

ELECTRIC POWER
1.6 newtons up
Field = 5.0x10^-3 Tesla
EMF = 30V
Frequency = 12.5 Hz
RMS Voltage = 57 V
C (the one where the amplitude got bigger and period got smaller)
2.5 A, 11 V, 2.2 V, 6W, 5.5W, 5.5W

LIGHT
Work function = 2.0eV
EK = 0.9eV
Transition goes from n=6 to n=something... it was the 13.2 to the 10.2 level
Velocity = 2.0x10^3m/s
Neutron diffracts slightly, though lambda/w<1, it was in same order of magnitude
Laser: B (wider gap = less diffraction, so that it's more bunched up)

SOUND
Out of phase, destructive interference, intensity
Frequency = 170Hz
Next Frequency = 510Hz
Intensity = 1.0x10^-6Wm^-2
C (8:1)
B (54dB)

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root

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Exam 2 Answer Thread
« Reply #2 on: November 14, 2007, 01:03:26 pm »
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Nice, think i got all those answers.

maxleng

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Exam 2 Answer Thread
« Reply #3 on: November 14, 2007, 01:07:13 pm »
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Quote from: "Spirited Sloth"
off the top of my head, i remember:

ELECTRIC POWER
1.6 newtons up
Field = 5.0x10^-3 Tesla
EMF = 30V
Frequency = 12.5 Hz
RMS Voltage = 57 V
C (the one where the amplitude got bigger and period got smaller)

LIGHT
Work function = 2.0eV
EK = 0.9eV
Transition goes from n=6 to n=something... it was the 13.2 to the 10.2 level
Velocity = 2.0x10^3m/s

Laser: B (wider gap = less diffraction, so that it's more bunched up)

SOUND
Out of phase, destructive interference, intensity
Frequency = 170Hz
Next Frequency = 510Hz
Intensity = 1.0x10^6Wm^-2
C (8:1)
B (54dB)


i got 9580 ms or something for the speed  :?

FUCK i also said they wouldn't diffract but i realise now they would arghhh

maxleng

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Exam 2 Answer Thread
« Reply #4 on: November 14, 2007, 01:10:15 pm »
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also what did people get for the Q for increasing slit width

i chose graph C, becuase the pattern would get larger? there would be no change in spacing as its slit 'width' but people are saying it gets thinner

boulos90

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Exam 2 Answer Thread
« Reply #5 on: November 14, 2007, 01:11:39 pm »
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Intensity in sound was 1x10^-6 i think

melodrama

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Exam 2 Answer Thread
« Reply #6 on: November 14, 2007, 01:13:46 pm »
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LOL yep. sorry, 1.0x10^6 would explode your ears.

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maxleng

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Exam 2 Answer Thread
« Reply #7 on: November 14, 2007, 01:20:40 pm »
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according to this Q (neap 2006)



a larger slit width has a larger pattern, and smaller width has a smaller pattern (note: spacing is still the same) which should give the answer C on our exam

melodrama

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Exam 2 Answer Thread
« Reply #8 on: November 14, 2007, 01:22:24 pm »
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but when you increase gap width, you increase w and thus ratio wavelength/w decreases and there's less diffraction, meaning that it'll bunch up... i dunno. i said C initially but i changed my mind.

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Ahmad

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Exam 2 Answer Thread
« Reply #9 on: November 14, 2007, 01:25:28 pm »
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I found that one tricky, but ended up putting B.
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Exam 2 Answer Thread
« Reply #10 on: November 14, 2007, 01:26:48 pm »
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since distancebetweenbands = (length * lambda) / widthofslit , and widthofslit increases, the distance between the bands will be smaller (ie, more bunched up)

Matt89

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Exam 2 Answer Thread
« Reply #11 on: November 14, 2007, 01:27:30 pm »
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Quote from: "Spirited Sloth"
2.5 A, 11 V, 2.2 V, 6W, 5.5W, 5.5W


Totally f***ed that one up. I stuffed up the calculation of the power, so I lost 3 marks  :(

v2shan

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Exam 2 Answer Thread
« Reply #12 on: November 14, 2007, 01:28:34 pm »
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Quote from: "maxleng"
according to this Q (neap 2006)

a larger slit width has a larger pattern, and smaller width has a smaller pattern (note: spacing is still the same) which should give the answer C on our exam


sry, but the answer for that is wrong, i checked with my tutor a few weeks ago

n spirited i got the same cept for the 2nd light q, were u meant to get the h value from the graph as well, cos i just used the 6.63E-34..... ooh i think thats y it was 3 marks, was it 3marks?... oh n u have very good memory
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melodrama

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Exam 2 Answer Thread
« Reply #13 on: November 14, 2007, 01:28:40 pm »
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i hate those power lines questions; they're so bitchy

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maxleng

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Exam 2 Answer Thread
« Reply #14 on: November 14, 2007, 01:28:49 pm »
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Quote from: "Matt89"
Quote from: "Spirited Sloth"
2.5 A, 11 V, 2.2 V, 6W, 5.5W, 5.5W


Totally f***ed that one up. I stuffed up the calculation of the power, so I lost 3 marks  :(


woah i got diff answers...i think cos i used a resistance of 4 ohms SHIT!!!!