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Reply 320
Original post by LegendX
someone must know how to do this question? Click on the original post link to see the question. Someone? Anyone? :smile:


Reason why I ask is I posted it earlier in the thread and it was overlooked also ^_^, must be really simple

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Reply 321
Original post by lucilleJR
could someone please explain to me why the answer to this question is A? thank you


ignore this I've just realised it's on this thread


I've seen this question too many times now. Just remember, V is constant so as a result if V = IR then V/I = R but if V is a constant, it would give you a graph in the form of 1/X = R and a 1/ X graph is a reciprocal graph so it looks like the graph in A.
Reply 322
For a standing wave on a wire, in the formulae L=nlambda/2, does L stand for length of wire, n for number of loops, lambda for standing wave wavelength?
Original post by krisshP
For a standing wave on a wire, in the formulae L=nlambda/2, does L stand for length of wire, n for number of loops, lambda for standing wave wavelength?


Yeah.
Reply 324
http://www.walter-fendt.de/ph14e/stwaverefl.htm

everyone see this. It makes the topic standing waves make sense
http://www.edexcel.com/migrationdocuments/QP%20GCE%20Curriculum%202000/June%202012%20-%20QP/6PH02_01_que_20120525.pdf

Ok guys a little help with 15 c) please?

' The smallest detail that can be seen on the image is half the length of the ultrasound
pulse. The thumbnail on the fetus is 0.50 mm thick. The speed of ultrasound in the
thumbnail is 2000 m s–1
.
Calculate the maximum pulse duration if the thumbnail is to be seen on the image'

What does it mean by pulse length, and how is that different to pulse duration? And how do we go about solving this problem?

Thanks a lot
Reply 326
does anyone on here know how to measure the rotation of the plan of polarisation and could explain to me please
Reply 327
Original post by GCSE-help
http://www.edexcel.com/migrationdocuments/QP%20GCE%20Curriculum%202000/June%202012%20-%20QP/6PH02_01_que_20120525.pdf

Ok guys a little help with 15 c) please?

' The smallest detail that can be seen on the image is half the length of the ultrasound
pulse. The thumbnail on the fetus is 0.50 mm thick. The speed of ultrasound in the
thumbnail is 2000 m s–1
.
Calculate the maximum pulse duration if the thumbnail is to be seen on the image'

What does it mean by pulse length, and how is that different to pulse duration? And how do we go about solving this problem?

Thanks a lot

One pulse length=1 wavelength

Speed=distance/time

The pulse goes to the end in the thumbnail AND back.

2000=0.001/ time

Time=0.001/2000

Time=5 X10^-7
Original post by Randy123
does anyone on here know how to measure the rotation of the plan of polarisation and could explain to me please


Yes I need this too...:redface:

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Reply 329
Original post by StUdEnTIGCSE
Yes I need this too...:redface:

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Pass polarised light from an LED through sugar. The sugar rotates the plane of polarisation. Place a polarising filter at the end of the sugar then rotate it until maximum intensity is detected by eye. Measure this rotation using a protractor to get the correct angle difference. More sugar concentration means more rotation of polarising filter, so measured angle difference from protractor is bigger.
Original post by Randy123
does anyone on here know how to measure the rotation of the plan of polarisation and could explain to me please


Have a look on the June 11 paper. A question was asked there.
Original post by krisshP
Pass polarised light from an LED through sugar. The sugar rotates the plane of polarisation. Place a polarising filter at the end of the sugar then rotate it until maximum intensity is detected by eye. Measure this rotation using a protractor to get the correct angle difference. More sugar concentration means more rotation of polarising filter, so measured angle difference from protractor is bigger.


How do we know what is original angle of plane of polarisation?

What is meant by the plane of polarisation? Is it the plane where the vibrations of the transverse wave is being confined to?
Reply 332
Is current ever inversely propertional to the voltage? :s-smilie:
Reply 333
Original post by StUdEnTIGCSE
How do we know what is original angle of plane of polarisation?

What is meant by the plane of polarisation? Is it the plane where the vibrations of the transverse wave is being confined to?

Say if plane of polarisation is horizontal, it means as unpolarised light passes through it, wave oscillations are restricted to the horizontal direction perpendicular to direction of wave travel.

Say if plane of polarisation is vertical, it means as unpolarised light passes through it, wave oscillations are restricted to the vertical direction perpendicular to direction of wave travel.

http://t1.gstatic.com/images?q=tbn:ANd9GcQx7LVjcRKKUWTSZtyMRVmD_bo4gUQ6y7mr_9IbMzolMudU4VvrKw
In there the first Polaroid has its plane of polarisation vertical.

http://www.arborsci.com/CoolStuff/Reyleigh_Diagram.jpg
Look at that
You choose the first Polaroid orientation, so you determine the original angle of polarisation which is likely to be 0* vertical as shown there.
Reply 334
Original post by Zoeyyy
Is current ever inversely propertional to the voltage? :s-smilie:


P=IV
I=P/V

So yes
Original post by krisshP
P=IV
I=P/V

So yes


Only if the power is constant :wink:

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Original post by krisshP
Say if plane of polarisation is horizontal, it means as unpolarised light passes through it, wave oscillations are restricted to the horizontal direction perpendicular to direction of wave travel.

Say if plane of polarisation is vertical, it means as unpolarised light passes through it, wave oscillations are restricted to the vertical direction perpendicular to direction of wave travel.

http://t1.gstatic.com/images?q=tbn:ANd9GcQx7LVjcRKKUWTSZtyMRVmD_bo4gUQ6y7mr_9IbMzolMudU4VvrKw
In there the first Polaroid has its plane of polarisation vertical.

http://www.arborsci.com/CoolStuff/Reyleigh_Diagram.jpg
Look at that
You choose the first Polaroid orientation, so you determine the original angle of polarisation which is likely to be 0* vertical as shown there.


Ah yes, get it now.
So the original angle of polarisation is determined beforehand, using a fixed polaroid orientation.
And the plane of polarisation is the plane in which the oscillations are being confined to perpendicular to the direction of travel of the wave.

Thanks

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Reply 337
Original post by StUdEnTIGCSE
Ah yes, get it now.
So the original angle of polarisation is determined beforehand, using a fixed polaroid orientation.
And the plane of polarisation is the plane in which the oscillations are being confined to perpendicular to the direction of travel of the wave.

Thanks

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Yep
Reply 338
can someone tell me how to do this question please?
mateo-6.jpg answer is c but how?
ignore the attatchment just the picture is necessary
(edited 10 years ago)
Reply 339
Original post by mnasmith
can someone tell me how to do this question please?
mateo-6.jpg answer is c but how?
ignore the attatchment just the picture is necessary


Go some pages back, the answer was posted with its explanation

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