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Physics: Post your doubts here!

hussamh10

hussamh10

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Wanzi21 said:
hi guys.. can u help me with this? :)
View attachment 11060
Click to expand...
  • first take out path difference
  • which is 28cm
  • the using v=f * lambda (By pythogras theoram)
    • 330= 1000(lambda)
    • and 330=4000(lambda
      • which are 33cm and 8.25 cm respectively
      • path difference for minima= (2n+1)(lambda/2)
      • putting n value as 0,1,2,3 we get 56cm, 18.7cm, 11.2cm nd 8 cm
      • since wavelength 56cm nd 8 r not within range of 8.25 to 33 so minima re waveleng 11.2 and 18.7. 2 minimas
 
Most_UniQue

Most_UniQue

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littlecloud11 said:
Yup. But the mark schemes are not always consistent. Here, they kept the answer to the same no. of sig. fig. as the data, but you'll notice that they don't always follow this.
So, even if you fail to keep it the same as the data, but give the answer to a reasonable number of sig fig. like 3, you won't be penalized. so relax. ;)
Click to expand...
tmx:D
 
littlecloud11

littlecloud11

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hussamh10 said:
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w10_qp_22.pdf
PLZ can any one expalin me the Q6 B part how to find the total resistance between A and B
Click to expand...

Ok, if the p.d. across AB is 4 vol then the p.d. across the 1.2k ohm resistor is 5 volt.
the ratio of the p.d. is the same as the ratio of the resistance between AB and the 1.2 kohm resistor
so, 4/5 = resistance across AB/ 1.2
resistance across AB = 4/5 * 1.2 = .96 kohm = 960 ohm
 
hussamh10

hussamh10

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how do we know that the ratio is same ??
Cant we do it by finding out the current supplied to thermistor and by finding out its resistance we can calculate the total resistance across AB
 
Saad (سعد)

Saad (سعد)

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As-Salaamu 'Alaykum wa Rahmatullah.

Someone please help me understand the concept of phase difference, and how a constant phase difference results in coherent waves.

I do have the general idea, but a revision could be useful, just so I don't miss anything. And a bit easy on the radians, please, I'm not a Math student. :D
 
Saad (سعد)

Saad (سعد)

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leosco1995 said:
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s05_qp_2.pdf
Q5 (b) (iii) please.
Click to expand...

In dsinϑ = nλ, ϑ is the angle between the diffracted ray and the grating's normal vector (the straight line from the centre of the grating - the normal zero order - to the screen).

If the light strikes at an angle, it will also leave at an angle (as shown in the diagram in the question). If we use the formula in this case, the value of ϑ would not be accurate, as the zero order of the diffracted light is bended upwards, while the formula assumes that the zeroth order is normal (a straight line between the grating and the screen).

That's what I understand. I don't get the Mark Scheme answer. o-o

Ratta we need. :cautious:
 
G

geek101

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Saad (سعد) said:
As-Salaamu 'Alaykum wa Rahmatullah.

Someone please help me understand the concept of phase difference, and how a constant phase difference results in coherent waves.

I do have the general idea, but a revision could be useful, just so I don't miss anything. And a bit easy on the radians, please, I'm not a Math student. :D
Click to expand...

first here is how you convert the degrees and radians...
radians to degrees : multiply by 180/π
degrees to radians: multiply by π/180

Phase difference is simply is the fraction of the cycle (the angle) by which one wave moves behind the other.
you can calculate is by using this equation: (with degrees)
360 (x/λ) where x is the difference in the distance between the two waves...
or 360(t/T) where the waves are out of step by time t.
use 2π for radians, since 360 = 2π

For coherent waves....they have a constant phase difference...this is usually the case with waves fron the same source. It does not matter whether the waves are in phase ....but coherent waves must have a constant phase difference...which means that the difference between them is the same throughout. They must also have the same wavelength and the same frequency.
this is quite brief..but hope it helps.
 
L

leosco1995

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geek101 said:
but arnt you supposed to talk about the specks of smoke particles?
Click to expand...
The question says "describe what is seen..", yes you do talk about the smoke particles, but since they appear as tiny, white specks of light you should mention that in the answer to that question since it's an observation. Likewise you would mention that the motion of these specks of light is haphazard since that is also an observation.
 
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geek101

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leosco1995 said:
The question says "describe what is seen..", yes you do talk about the smoke particles, but since they appear as tiny, white specks of light you should mention that in the answer to that question since it's an observation. Likewise you would mention that the motion of these specks of light is haphazard since that is also an observation.
Click to expand...

thnx got it...and i also read that the smoke particles are not what you see but the light reflected from them....thnx sista!
 
iKhaled

iKhaled

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geek101 said:
first here is how you convert the degrees and radians...
radians to degrees : multiply by 180/π
degrees to radians: multiply by π/180

Phase difference is simply is the fraction of the cycle (the angle) by which one wave moves behind the other.
you can calculate is by using this equation: (with degrees)
360 (x/λ) where x is the difference in the distance between the two waves...
or 360(t/T) where the waves are out of step by time t.
use 2π for radians, since 360 = 2π

For coherent waves....they have a constant phase difference...this is usually the case with waves fron the same source. It does not matter whether the waves are in phase ....but coherent waves must have a constant phase difference...which means that the difference between them is the same throughout. They must also have the same wavelength and the same frequency.
this is quite brief..but hope it helps.
Click to expand...
after readin this i felt i know nothing about waves LOL!
 
hmlahori

hmlahori

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http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w10_qp_21.pdf
http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w10_ms_21.pdf
Q 2(b) and Q 6(a ii) Can someone show exactly how these both are drawn? i have read the mark scheme and examiner report but i might be thinking it is drawn some other way entirely so just to verify my own drawings.

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w09_qp_21.pdf
http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w09_ms_21.pdf
Q 7(b) in this i also want to confirm if my drawing is correct so if someone else can show the correct one..
 
Saad (سعد)

Saad (سعد)

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Okay...

In the syllabus, we have:

(e) describe the effect of a uniform electric field on the motion of charged particles.

And in the notes, I have things like Equipotential Surface, Potential Gradient, and 'Electric field lines must meet the surface at right angles'.

... What in the realm of Physics is this?
 
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