Physics: Post your doubts here!

[darkpichu]

Please help with question 4

http://www.xtremepapers.com/CIE/index.p ... 8_qp_4.pdf

 

[Dayyanah]

hey everyone
i need some help
can anyone bother to explain how the double slit experiment works? i tried reading a few pages but dont seem to be getting a hang of it
thanx in advance

 

[rz123]

a coherent light source such as a laser beam illuminates a thin plate pierced by two parallel slits, and the light passing through the slits is observed on a screen behind the plate. The wave nature of light causes the light waves passing through the two slits to interfere, producing bright and dark bands on the screen — a result that would not be expected if light consisted strictly of particles. However, at the screen, the light is always found to be absorbed as though it were composed of discrete particles or photons. This establishes the principle known as wave–particle duality.

light is passed thru two slits simply to observe the interference pattern on the screen. you will observe some dark and some bright fringes. bright fringe represent constructive interference and dark fringes represents destructive interference respectably.

The source emits monochromatic light.(comprising waves of one frequency only)

The single slit ensures that the light waves incident on the double slits are coherent.
Coherent sources must have same frequency and constant phase difference. Constant phase difference means that the two sources always differ in phase by the same amount.


, X is only valid for values of D>>a and when is very small. This equation cannot be used for diffraction grating!



Factors affecting appearance of fringes due to double slit interference of light:

If the single slit together with the light source is moved closer to the double slits, the bright fringes produced are brighter as the intensity of the light passing through the double slit is greater. The fringe separation remains the same.
If one of the slit is closed, a different pattern is obtained. The central maximum is now much brighter and broader compared to the other maxima at the sides. This is the diffraction pattern for single slit.
If white light is used, the central fringe is white and the fringes on either side are coloured. Recall that , so . Blue is the colour nearer to the central fringe and red is farther away.
If the space between the double slit and screen is filled with a transparent medium of refractive index higher than that of air or vacuum, the fringes produced on screen will be narrower. This is because the wavelength is smaller in a medium where the refractive index is higher than that of air or vacuum.

The following video can help you understand: (I recommend that you stop at 1 min 50 seconds of the video unless you understand wave-particle duality)

this will make it even more clear:-
http://www.youtube.com/watch?v=DfPeprQ7 ... r_embedded

 

[Emily793]

@ darkpichu hope this helps you understand Q4 plz bear the handwritting with me!

 

[Karimgenena]

http://www.xtremepapers.com/CIE/Interna ... 7_qp_4.pdf

Q 2(c)ii

 

[Dayyanah]

@ rviboy thanks alot

 

[rz123]

^ur welcome

 

[Dayyanah]

need help

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s11_qp_11.pdf

qn 31

i want someone to tell me how its done

thanx

 

[unique840]

need help

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s11_qp_11.pdf

qn 31

i want someone to tell me how its done

thanx

charge = current * time
charge = 10 * 1
= 10 coulumbs

total charge passing through the wire is 10 C
charge of electrons is 1.6 * 10^-19
number of electrons = total charge / electron charge
= 10 / (1.6 * 10^-19)
= 6.25 * 10^19
= 6.3 * 10^19 (option C)

 

[hikarigenzo]

Hi, can you tell me why 6b (i) is 0A? Is it because of short circuit?

Can you also explain to me 7b (ii)?

Thanks

http://www.xtremepapers.com/CIE/Interna ... _qp_22.pdf

 

[OakMoon!]

Hi, can you tell me why 6b (i) is 0A? Is it because of short circuit?

Can you also explain to me 7b (ii)?

Thanks

http://www.xtremepapers.com/CIE/Interna ... _qp_22.pdf

When the jockey is at A, there will be no load parallel to A in the circuit, hence, the voltage will be 0 V which mean there will be no current flowing through the ammeter. The voltage in A is equal to the voltage in the resistance wire given that both of them are parallel. So voltage and current in Ammeter will be 0.

For 7b ii) It's a simple matter of conservation of energy. The mass energy of the reactants is less than the ME of the products. So there must be some extra energy in the reactants that must be there to maintain conservation of energy. This energy is the kinetic energy of the alpha particle before it bombards.

For velocity just use (1/2)mv².

 

[rz123]

http://www.xtremepapers.com/CIE/Interna ... _qp_22.pdf
M/J 2010 p 22

4 c part. cnt get any clue from marking scheme

 

[OakMoon!]

You need to recall the concept of stationary wave formation in an open end tube. At the FUNDAMENTAL frequency (The lowest frequency at which sound is heard) the wave formed within L is 1/4 of the complete wavelength as show in the picture. So you'll take the wavelength and use it to find the frequency.

 

[rz123]

thanks a lot brother for reminding me the relevant concept here!!! but still i can't figure out the solution. L/4 is = .15m right so v/ lambda = frequency it gives 2200Hz nd ms says 180Hz. ms is wrong i think

 

[OakMoon!]

When at the lowest frequency a new wavelength will be there so we will use the new wavelength. L is equal to 1/4 lamda. So 4*L will be equal to the new wavelength. 4*0.45=1.8m
330/1.8=180

Hope this helped.

 

[rz123]

i got it somehow. like the previous wavelength was at highest frequency nd for lowest fundamental frequency it will be 4 times more then that. memorized it. thanks bhaii !

 

[OakMoon!]

No use to memorize this. The concept of the the open tube will be enough to deal with such problems. Just look at the drawing I made? Isn't that a quarter of a wavelength? The calculations follow that path.

 

[rz123]

ooooohh i got it completely bro but just one lil thing how this new complete wavelength will get us the lowest frequency..like how does a 1 complete wavelength in the tube column gives always a lowest frequency sound. :sorry:

 

[OakMoon!]

How did you get it completely? And I didn't get your question. Frequency is inversely proportional to wavelength. The greater the wavelength, the smaller the frequency. The speed remains same in the equation f=c/lamda and so you get the lowest F with greatest wavelength. You need to open the book and revise the concept of stationary waves before you ask anymore questions.

 

[Dayyanah]

hey, can anyone help me with any sort of phy AS notes? i dont feel like reading the text book anymore
thnx