Physics Pp:3-Variant 2- Discussing Answers!!

[JOEJOE]

No its 1.56 angle of incidence = 40deg anyway how the hell can the ref indx of a glass be 1.3..... its always 1.5 ... And if i wrote for the generator question... to add a commutator which will allow current to be induced bothways.. will that be correct?? BTW power is 4.5W..

 

[BumbleBEA]

No its 1.56 angle of incidence = 40deg anyway how the hell can the ref indx of a glass be 1.3..... its always 1.5 ... And if i wrote for the generator question... to add a commutator which will allow current to be induced bothways.. will that be correct?? BTW power is 4.5W..

OH MY GOD! A COMMUTATOR. Darnit! I completely forgot....

 

[B333]

That seems correct i just made up the answer and wrote use a step-up transformer for some reason

 

[kboss]

No its 1.56 angle of incidence = 40deg anyway how the hell can the ref indx of a glass be 1.3..... its always 1.5 ... And if i wrote for the generator question... to add a commutator which will allow current to be induced bothways.. will that be correct?? BTW power is 4.5W..

nt sure abt the generator one i think the simple thing is for it to be able to turn both ways.
i messed up the power question...how silly of me
i put 180 which was for the whole circuit not for one lamp....

 

[JOEJOE]

Ahahaaha i finally beat the smart girl in something!!!!

 

[B333]

What about the shirts questions which ones dried first and why does wetting your hair help cool you down?

 

[B333]

Yeah i wrote 180 watts then changed to 4.5 watts then changed again to 180 watts ugh so annoying

 

[BumbleBEA]

Ahahaaha i finally beat the smart girl in something!!!!

Smart? You flatter me~<3

 

[kboss]

What about the shirts questions which ones dried first and why does wetting your hair help cool you down?

the shirt in the wind....cuz wind helps molecules evaporate and the unfolded short cuz it has a greater surface area.
it helps u cool cuz as most energetic molecules evaporate the avg. speed of remaining molecules falls and u feel cool.

 

[B333]

What do you think the grade boundaries will be like? I just hope its under 40 for an A it was a really tough paper
I have paper 52 on Tuesday wish me luck I seriously don't know why I chose to do the practical paper
is anyone else doing paper 5 and if so how did you revise?

 

[B333]

Finally some correct answers!

 

[n0n4m3]

waves in shallow water are faster than in deep water.

Waves in shallow water move slower than in deep water due to greater resistance in shallow water.

 

[kareem]

I'm afraid not. The answer is indeed 1.56, approximately.

*refractive index of air=1*

refractive index 1 x sin theta 1= refractive index 2 x sin theta 2

The angle of incidence from the air to the glass was 90 degrees, and the angle of refraction once it entered the glass was 40 degrees.

Thus:

1 x sin 90= refractive index of glass x sin 40

refractive index of glass= sin 90 / sin 40

=1.555.... or 1.56 (3 significant figures)

Note: The angle is 40 degrees, not 50 degrees because you must measure it relative to the normal.

i think you got the angle of incidence rong , its "sin i / sin r" and angle i was either 40 or 50 i cant remember what i wrote so sin40/sin90 or sin 50/sin 90 is the right answer im sure AND you used the formula rong angle of incidence wasnt 90

 

[kareem]

do this....
sin of critical angle = 1/ refractive index
i.e reflective index = 1/ sin of critical angle
and angle of refraction wasn't given too....
plus the refractive index has to be more than one if it is a denser medium than air...which i suppose glass is

<r was 90 degree u can see it on the drawing

 

[Chucky]

yes but for some reason its
sinr/sin i since it now travels from optically dense to less dense.
otherwise your answer is 0.6 (which is what I got, but i know i'm wrong)

sinr = sin90
sin i= sin40
answer should be 1.56 and from common knowledge, glass is always around 1.5

 

[Chucky]

That's a shame, but I'm sure you'll get some effort marks!

I made quite careless mistakes as well.

For the lightbulb question, I made it all the way until 40-31.7, and my idiot self calculates wrong and wrote:

40=31.7=9.3 <---FOR THE LOVE OF GOD, WHY?!

Haha... so I put 9. What a shame.

they should have a range
or they will only award full marks for 8 or 9 bulbs because some people thought 31.7 should be 31 -___-

 

[kareem]

yes but for some reason its
sinr/sin i since it now travels from optically dense to less dense.
otherwise your answer is 0.6 (which is what I got, but i know i'm wrong)

sinr = sin90
sin i= sin40
answer should be 1.56 and from common knowledge, glass is always around 1.5

dude we weren't taught that the formula changes when medium is different but idk i hope its right cause i dont think that it ever changes

 

[omglaigcse]

refractive index = 1 / sin c
critical angle was 40
so 1/sin40 = 1.56

 

[BumbleBEA]

dude we weren't taught that the formula changes when medium is different but idk i hope its right cause i dont think that it ever changes

i think you got the angle of incidence rong , its "sin i / sin r" and angle i was either 40 or 50 i cant remember what i wrote so sin40/sin90 or sin 50/sin 90 is the right answer im sure AND you used the formula rong angle of incidence wasnt 90

Please refer to the answers above, it's basically just rearranging the equation. This is one of the few questions I'm actually confident about.

 

[BumbleBEA]

they should have a range
or they will only award full marks for 8 or 9 bulbs because some people thought 31.7 should be 31 -___-

I certainly hope so! >__<