Physics: Post your doubts here!

[meobunny]

I thought shayad isse kisi ka bhala hojaye Allah hum sab ko A grade se nawazain, AAMMEEENN

 

[Warrior66]

Asalam-o-Alaikum! (reposting this question again)
is it true that the brightness of the fringes increases by increasing the width of both the slits without changing the separation 'a' between the slits? I thought that narrowing the slits makes the fringes brighter?
If its not too much trouble, could you please tell me all the relationships concerning the diffraction grating that the examiners frequently ask us about?
gary221?
Thanks a bunch!!

 

[gary221]

Asalam-o-Alaikum! (reposting this question again)
is it true that the brightness of the fringes increases by increasing the width of both the slits without changing the separation 'a' between the slits? I thought that narrowing the slits makes the fringes brighter?
If its not too much trouble, could you please tell me all the relationships concerning the diffraction grating that the examiners frequently ask us about?
gary221?
Thanks a bunch!!

think abt it this way. As u increase the width u let in more light thus at the point previously where u had constructive interference, over there now more waves will coincide due to the widening of the gaps. Thus the brightness increase.

 

[Warrior66]

gary221, I did come across the answer you posted above but I didn't quite get it...could you please answer it for me?

 

[qasim ch]

Physics p2 cancelled in pakistan due to official holidays from 9 to 13 May. Does anyone know that now on what date the paper will be conducted....?

 

[gary221]

Determining wavelength using a grating ---> d sinΘ = n
whr d = distance btw adjacent lines on the grating.
n = order of the maximum. only has 2 integer values (0, 1, 2, 3)

normally, they dont give u d outright...
bt sth like " the grating has 3000 lines per cm" ---> n u have 2 calculate d from this
ie d = 1 cm/no. of lines
d = 1/3000 = 3.33 * 10^-6 m

 

[Warrior66]

Determining wavelength using a grating ---> d sinΘ = n
whr d = distance btw adjacent lines on the grating.
n = order of the maximum. only has 2 integer values (0, 1, 2, 3)

normally, they dont give u d outright...
bt sth like " the grating has 3000 lines per cm" ---> n u have 2 calculate d from this
ie d = 1 cm/no. of lines
d = 1/3000 = 3.33 * 10^-6 m

Thank you!

 

[gary221]

gary221, I did come across the answer you posted above but I didn't quite get it...could you please answer it for me?

M not giving AS this yr..bt let me try..

when u increase the width of the slits ---> more light now enters thru them.
So, both the interferences will increase as now more light = move waves = more constructive as well as destructive interfernces will take place.
ie more waves will coincide ---> leading to brighter fringes(as well as darker fringes).

Decreasing width increases sharpness of the fringes...nt brightness.
as light is not spread out..fringes will be sharper, but since lesser waves now coincide --> fringes will b less bright!!

Hope u gt it!!

 

[1357913579]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s09_ms_2.pdf
5(B)
pleasee someone

 

[Warrior66]

M not giving AS this yr..bt let me try..

when u increase the width of the slits ---> more light now enters thru them.
So, both the interferences will increase as now more light = move waves = more constructive as well as destructive interfernces will take place.
ie more waves will coincide ---> leading to brighter fringes(as well as darker fringes).

Decreasing width increases sharpness of the fringes...nt brightness.
as light is not spread out..fringes will be sharper, but since lesser waves now coincide --> fringes will b less bright!!

Hope u gt it!!

Jazaka'Allahum Khairan!

 

[mrnt3250]

Using laws of Kirchhoff, solve for the values of I1, I2 and I3.
==
I have got the concept for kirchhoff's law and stuff, but then this question is confusing for me.
Please explain step by step.
Thanks in advance.

 

[mrnt3250]

Jazaka'Allahum Khairan!

This type of question has always been a disaster for me
Can you write all the possible effects of changes to the apparatus? (The ones you said, and also other changes like moving the screen further, changing wavelength, changing slit separation, etc.)

 

[Areeba Shahnawaz]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w05_qp_2.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w05_ms_2.pdf
umm... plz explain question 5 part ci n cii as im unable to understand them from the mark scheme part cii can be done by ratio method too but I cant work it out so plz help with it

u need 2 find out k for wave A in terms of I. (I=ka2) then substitute this value of k in I'=ka2_formula for wave B. amplitude is read from the waveforms displaced. the new intensity of wave B is I'

 

[goodluckayesha]

u need 2 find out k for wave A in terms of I. (I=ka2) then substitute this value of k in I'=ka2_formula for wave B. amplitude is read from the waveforms displaced. the new intensity of wave B is I'

thnq

 

[goodluckayesha]

Thank youuuu so much!

did u understand??
ur most welcum

 

[1357913579]

Jazaka'Allahum Khairan!

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_qp_2.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_ms_2.pdf
in this question 5c(ii) in ms its written theres no effect on brightness how?
because i totally agree with gary's statement

 

[goodluckayesha]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_qp_2.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_ms_2.pdf
in this question 5c(ii) in ms its written theres no effect on brightness how?
because i totally agree with gary's statement

the separation of slits is increased not the width of each slit so brightness wud remain same

 

[1357913579]

the separation of slits is increased not the width of each slit so brightness wud remain same

 

[goodluckayesha]

0.7 is the slit separation n the 2 small holes r the slits
so whts the doubt??

 

[1357913579]

0.7 is the slit separation n the 2 small holes r the slits
so whts the doubt??

my labeling is correct for showing which one is the width?
becuase if the its correct then if u increase the slit seperation than the distance between the slits( slit width) decreases isnt it? so