Physics: Post your doubts here!

[Suchal Riaz]

http://papers.xtremepapers.com/IB/Physics/Higher/2008 May/Physics HL paper 1 TZ2.pdf
Can someone explain Q7.

There are two tricks in this question. First thing is that it is a length force graph not extension force. So the area Y represent the energy. But Y is not in option. That is second trick. That the area Z is equal to Y clearly. As diagonal of a rectangle cut it into two equal triangles.
Therefore answer is C

 

[Suchal Riaz]

Which topics are important in Magnetism portion? I mean which ones should we prepare for O Level Exams?

This is A level thread. Not for o level, kid.

 

[Maganius]

This is A level thread. Not for o level, kid.

Ops lol my bad
Sorry

 

[ahmed abdulla]

Q . 4 c(ii) .. why its negative ?

 

[lawman]

forces notes

 

[Suchal Riaz]

This question 5 of CIE A-LEVELS of 9702/02/O/N/07 (PHYSICS ouc/nov. 2007)

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_qp_2.pdf

"(c) State the effect, if any, on the appearance of the fringes observed on the screen when the following changes are made, separately, to the double-slit arrangement in (b).
(i) The width of each slit is increased but the separation remains constant.
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
............................................................................................................................. [3]"

My response:
As the INTENSITY is inversely proportional to the AREA , so on increasing width of the slit(AREA) the INTENSITY decreases. As INTENSITY is directly proportional to the (AMPLITUDE)^2 so Amplitude also decreases.
Thus bright fringe becomes less bright, dark remain the same and off course there is no effect on fringe width as fringe separation remains same.

Answer in Marking Scheme:

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_ms_2.pdf

(c) (i) same separation B1
bright areas brighter (1) dark areas, no change (1)
(allow ‘contrast greater’ for 1 mark if dark/light areas not discussed)
fewer fringes observed (1) any two, 1 each


What I dont understand is how bright fringe get brighter and how come there are fewer fringes observed, according to answer???

Please explain...

The intensity is inversely proportional to area on which it falls not through which it passes. As the bright fringes would be the same distance apart as fringe separation and distance of screen is unchanged., the area at which the light falls would be the same. But now only difference is that more light passes through the fringes and still falls on the same area. So wouldn't the intensity increase?
Lets say a windows illuminates your room and it's left half opened. it is dark(low intensity) in your room. So you decided to open your windows. You room's surface area remains same and you open you windows full. Now more light enter through it. So it will be brighter in your room.

 

[Suchal Riaz]

Q . 4 c(ii) .. why its negative ?

The positive charge will attract negative charge. As the container is earthed which is at zero potential, negative charge will flow towards the positive potential induced on the container.

 

[Suchal Riaz]

Q . 4 c(ii) .. why its negative ?

If i am wrong then sorry i am just an As level student.

 

[ahmed abdulla]

If i am wrong then sorry i am just an As level student.

According to the AS knowlege you are right >
but to gain three marks you should talk about work and how potential differs

 

[UXm@N]

The intensity is inversely proportional to area on which it falls not through which it passes. As the bright fringes would be the same distance apart as fringe separation and distance of screen is unchanged., the area at which the light falls would be the same. But now only difference is that more light passes through the fringes and still falls on the same area. So wouldn't the intensity increase?
Lets say a windows illuminates your room and it's left half opened. it is dark(low intensity) in your room. So you decided to open your windows. You room's surface area remains same and you open you windows full. Now more light enter through it. So it will be brighter in your room.

Thanks.. Nicely explained..

 

[Mohammad M]

Salams.
I am stuck in chapter 1
Could you explain the end chapter answer to 1c, 2b and 2c?
JazakAllah Khair

 

[U7X0GXO]

Salams.
I am stuck in chapter 1
Could you explain the end chapter answer to 1c, 2b and 2c?
JazakAllah Khair

wsalam
LOL..
-What is chapter 1?
-What are the questions?

 

[Hassan Ali Abid]

Thanks a lot Hassan!...for P4 does it help to memories the mark schemes as well?....and in P5 are you supposed to answer in point form or paragraphs?

For phy applications memories each and everything in the ms ...like the ans of all essay/long questions ....and for core syllabus learn the definations from ms ..not from the book.
For p5 dont attempt the Q1 in point form.

 

[UXm@N]

This question 5 of CIE A-LEVELS of 9702/02/O/N/07 (PHYSICS ouc/nov. 2007)

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w07_qp_2.pdf

"(c) State the effect, if any, on the appearance of the fringes observed on the screen when the following changes are made, separately, to the double-slit arrangement in (b).
(i) The width of each slit is increased but the separation remains constant.
...........................................
...........................................
...........................................
........................................... [3]"

My response:
As the INTENSITY is inversely proportional to the AREA , so on increasing width of the slit(AREA) the INTENSITY decreases. As INTENSITY is directly proportional to the (AMPLITUDE)^2 so Amplitude also decreases.
Thus bright fringe becomes less bright, dark remain the same and off course there is no effect on fringe width as fringe separation remains same.

Answer in Marking Scheme:

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w07_ms_2.pdf

(c) (i) same separation B1
bright areas brighter (1) dark areas, no change (1)
(allow ‘contrast greater’ for 1 mark if dark/light areas not discussed)
fewer fringes observed (1) any two, 1 each


What I dont understand is how bright fringe get brighter and how come there are fewer fringes observed, according to answer???

Please explain...

 

[UXm@N]

Koi toh reply karo..!!

 

[Hassan Ali Abid]

Koi toh reply karo..!!

bro if u are havaing the pacific book 2 then see that ...its explained in detail in that book.

 

[UXm@N]

bro if u are havaing the pacific book 2 then see that ...its explained in detail in that book.

I dont have that... :/ !!! It would be good I anyone can expalin here....!!! Thanks..

 

[Suchal Riaz]

This question 5 of CIE A-LEVELS of 9702/02/O/N/07 (PHYSICS ouc/nov. 2007)

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_qp_2.pdf

"(c) State the effect, if any, on the appearance of the fringes observed on the screen when the following changes are made, separately, to the double-slit arrangement in (b).
(i) The width of each slit is increased but the separation remains constant.
...........................................
...........................................
...........................................
........................................... [3]"

My response:
As the INTENSITY is inversely proportional to the AREA , so on increasing width of the slit(AREA) the INTENSITY decreases. As INTENSITY is directly proportional to the (AMPLITUDE)^2 so Amplitude also decreases.
Thus bright fringe becomes less bright, dark remain the same and off course there is no effect on fringe width as fringe separation remains same.

Answer in Marking Scheme:

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_ms_2.pdf

(c) (i) same separation B1
bright areas brighter (1) dark areas, no change (1)
(allow ‘contrast greater’ for 1 mark if dark/light areas not discussed)
fewer fringes observed (1) any two, 1 each


What I dont understand is how bright fringe get brighter and how come there are fewer fringes observed, according to answer???

Please explain...

i explained it earlier. didn't you get it? what problem u are having in it. we can discuss.

 

[UXm@N]

i explained it earlier. didn't you get it? what problem u are having in it. we can discuss.

I understood that why brightness is increasing..!! But tell me why less fringes are formed. ..!!

 

[Suchal Riaz]

I understood that why brightness is increasing..!! But tell me why less fringes are formed. ..!!

The central fringe is most brightest. And then the second one is less bright. And so on. So the last couple of fringes we see are very very less bright.
As now the overall brightness increase, we are able to see those fringes which otherwise wouldn't be visible to us as their brightness would be extremely small.