Biology; Chemistry; Physics: Post your doubts here!

[AtemisDelta]

tadaaa!!!!!!!!!!!!!! finally got uploaded. hope u find it useful
need further help u can pm me

 

[awaisbuttrocksCIE]

give me notes of natural vegetative propogation..PLEASE? anybody and CRO in Physics? Please

 

[SalmanPakRocks]

give me notes of natural vegetative propogation..PLEASE? anybody and CRO in Physics? Please

For CRO let me explain it to you.


Ok so.
Lets first thing you wanna know is what thermionic emission actually is.
well Thermionic Emission is the name given to the fact that when metals are provided with heat the free valence electrons escape from the metal.

Ok lets consider the diagram now.
First thing which is present in the CRO is a battery connected to Filament (it provides a lot of heat when electricity is passed through it) Then the heat from the filament causes thermonic emission to happen as the metal is place near it. This makes the electrons come out and form a electron gun. The electron gun is then passed through a plate called cathode (-ve charged) and it acts as a brightness controller, this is because we can control the number of electrons following through that plate. If we want more brightness we can set the potential of charge of that plate low and vice versa for low brightness. Anyhow, then the electrons move towards Anodic plate (+ve charged). It is attached to the both side of the CRO, and hence is used to accelerate the speed of electrons. Then the electrons move towards the X-plate and Y-plate which causes Oscillatory movements to be displayed in the screen. Finally the electrons hit the Flouroscent screen which is covered with Zinc sulphite and causes colours to display, the potential energy of the electrons causes the movements to be displayed on the screen.
I hope i m correct, hope I made it clearer to u, anyways if u still have doubt i will be happy to answer that.

P.S: There is Vaccum in the CRO to avoid the air molecules colliding with electrons.

 

[legion]

give me notes of natural vegetative propogation..

i hope this helps. its mostly from Wikipedia but edited as to stuff that includes our syllabus.

 

[scouserlfc]

I wanted to ask if we can react a radioactive element like Francium with acids or not
cause our chemistry teacher said we cannot do reactions with radioactive elements

They are too dangerous as i think for even handling them reacting them openly yeah can be very dangerous and shudnt be done !

 

[Abdullah Yousuf]

Ofcourse we can't. I mean Francium is HIGHLY reactive metal and reacting it with Acid can cause Major blast.

Thanks.....

 

[legion]

is it possible for refractive index of an object to be less then 1? reason???

 

[Abdullah Yousuf]

is it possible for refractive index of an object to be less then 1? reason???

Yes it is possible!
In typical media such as glass, air, water, perspex etc, one expects to find a refractive index greater than one. Light travels through the medium by sequential absorption and re-emission by the particles in the media. Think of atoms as passing a photon along like a package in a human chain. It takes time for each atom to absorb and re-emit the photon so the speed of light is slower than in vacuum. The ratio of speed in and out of the media is the refractive index. So in almost all cases the refractive index is grater than one.

However there are some cases where the refractive index of a media can be less than one.

Plasma - the refractive index of plasma is less than one n(f)= [1-(w/f)^2]^1/2
Where n(f) is the refractive index as a function of the frequency of light which is propagating through the plasma, w = the plasma frequency.

Metals - although not transparent at visible frequencies, metal is transparent to IR frequencies, and exhibits an index less than one. This is because there is a more complex mechanism used by the atoms to pass the photon through the medium. In conductors like metal, its very complicated as magnetism and moving electrons in atoms become important.

NOTE: It is the phase velocity that becomes faster than the speed of light. The group velocity of light can never exceed the speed light! Information and energy travels with the group velocity and so violation of relativity or Maxwell's equations.


hope its not too complex

Source:http://wiki.answers.com/Q/Is_it_possible_to_have_a_refractive_index_less_than_one

 

[legion]

Yes it is possible
hope its not too complex

thancx
no its not.

 

[hassan100]

Yes it is possible!
In typical media such as glass, air, water, perspex etc, one expects to find a refractive index greater than one. Light travels through the medium by sequential absorption and re-emission by the particles in the media. Think of atoms as passing a photon along like a package in a human chain. It takes time for each atom to absorb and re-emit the photon so the speed of light is slower than in vacuum. The ratio of speed in and out of the media is the refractive index. So in almost all cases the refractive index is grater than one.

However there are some cases where the refractive index of a media can be less than one.

Plasma - the refractive index of plasma is less than one n(f)= [1-(w/f)^2]^1/2
Where n(f) is the refractive index as a function of the frequency of light which is propagating through the plasma, w = the plasma frequency.

Metals - although not transparent at visible frequencies, metal is transparent to IR frequencies, and exhibits an index less than one. This is because there is a more complex mechanism used by the atoms to pass the photon through the medium. In conductors like metal, its very complicated as magnetism and moving electrons in atoms become important.

NOTE: It is the phase velocity that becomes faster than the speed of light. The group velocity of light can never exceed the speed light! Information and energy travels with the group velocity and so violation of relativity or Maxwell's equations.


hope its not too complex

Source:http://wiki.answers.com/Q/Is_it_possible_to_have_a_refractive_index_less_than_one

arent u taking at a little higher level.There is no need to go in such detail in olevels i guess

 

[snowbrood]

e) suggest a suitable method for investigating the effect of a given variable on the speed of a reaction.... i dont understand what does this part means

 

[Abdullah Yousuf]

arent u taking at a little higher level.There is no need to go in such detail in olevels i guess

Yep You are right
Sorry about that

 

[SalmanPakRocks]

e) suggest a suitable method for investigating the effect of a given variable on the speed of a reaction.... i dont understand what does this part means

please give full question so i maybe able to help.

 

[sweetiepie]

Might help u

http://ratesofreaction.wordpress.com/

 

[snowbrood]

please give full question so i maybe able to help.

http://www.scribd.com/doc/56077784/Speed-of-Reaction can u tell me where to find this type of documents i mean the one from singapore 5072

 

[snowbrood]

can anyone tell me where to find 5072 chemistry singapore sw files please help me because it has notes in this one of these docs is above

 

[CaptainDanger]

can anyone tell me where to find 5072 chemistry singapore sw files please help me because it has notes in this one of these docs is above

http://www.scribd.com/doc/38821401/Chemistry-Air-Atmosphere-Syllabus-notes

http://www.scribd.com/doc/38755971/Organic-Chemistry-Syllabus-Notes

http://www.scribd.com/doc/40235202/Chemistry-Finalized-Notes

There is difference though... So don't confuse yourself when you see anything which isn't from your syllabus...

 

[snowbrood]

http://www.scribd.com/doc/38821401/Chemistry-Air-Atmosphere-Syllabus-notes

http://www.scribd.com/doc/38755971/Organic-Chemistry-Syllabus-Notes

http://www.scribd.com/doc/40235202/Chemistry-Finalized-Notes

There is difference though... So don't confuse yourself when you see anything which isn't from your syllabus...

luckly even i found the same files thanks anyways man... but so far there is negligible difference between the two or i believe there is no difference as i saw there syllabus it is exactly the same as ours(though i didnt go through full syllabus)

 

[CaptainDanger]

^ Its good then...

 

[snowbrood]

N2+h2-----Nh3 In this reaction increase in pressure will increase both the yield of ammonia (because in forward reaction less number of moles are formed)
can anyone explain me this