Exam 2 Answer Thread

[melodrama]

Post answers here. I wrote them on my formula sheet but the ladies TOOK IT AWAY.

[melodrama]

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)

[root]

Nice, think i got all those answers.

[maxleng]

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]

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]

Intensity in sound was 1x10^-6 i think

[melodrama]

LOL yep. sorry, 1.0x10^6 would explode your ears.

[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

[melodrama]

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.

[Ahmad]

I found that one tricky, but ended up putting B.

[___]

since distancebetweenbands = (length * lambda) / widthofslit , and widthofslit increases, the distance between the bands will be smaller (ie, more bunched up)

[Matt89]

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]

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

[melodrama]

i hate those power lines questions; they're so bitchy

[maxleng]

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!!!!