The Ultimate AS Physics Thread

[Hateexams93]

why the brightness decreases when the wavelenght increases ?????????????????????????????

 

[Zenzenzen]

why the brightness decreases when the wavelenght increases ?????????????????????????????

It doesn't! It only increases if you increase intensity or increase the separation of the slits! Or use a brighter light

 

[Hateexams93]

ITS written in the marking scheme

 

[Zenzenzen]

Which question? can you send me the links

 

[Hateexams93]

http://www.xtremepapers.me/CIE/Internat ... B5%2B6.pdf this are the answers , may june 2003 question 4

 

[Zenzenzen]

You're right o.o
No idea how wavelength is connected to the brightness

 

[aliya_zad]

The (b) part please..............

Speed will remain the same.
Explanation-
Speed depends on the voltage. In this question voltage and the charge is constant throughout.According to the equation voltage=wd/charge if voltage is the same wd will also be the same. Therefore kinetic energy is constant and hence the speed remains the same.
Hope this helps!

 

[Hateexams93]

so why the brightness decreases when the wavelenght increases ?? can some1 plz expain it ?

 

[hassam]

HOW DOES INCREASING SLIT width LEADS TO broadening OF fringes.....?

 

[Hateexams93]

HATE WAVES -.- is there is a topic , where we can find the explanations to all of this ?

 

[Hateexams93]

r u sure about it , because i read somewhere that its because increasing the wavelenght increases the width of the fringes , but WHY ?

 

[crystallinescar]

r u sure about it , because i read somewhere that its because increasing the wavelenght increases the width of the fringes , but WHY ?

Yes, that is absolutely correct. So you can look it that way as well, thinking of energy being 'spread' across a larger surface area, so lesser energy per unit area.

This will help:
http://vsg.quasihome.com/interfer.htm

 

[Zenzenzen]

HOW DOES INCREASING SLIT width LEADS TO broadening OF fringes.....?

Just think about it logically. Imagine shining a flashlight through a hole in the wall. On the other side, the point of light will by very small. However, when you make the hole bigger, the point of light on the other wall also gets wider! Hope this helps

 

[Hateexams93]

what affect has increased split separatin on brightness of the fringes ?

 

[Hateexams93]

oohhh i got the answer nm )

 

[sasukeuchiha]

It does. brightness decreases when the wavelength increases.

As wavelength increases, the light from the same slit (of same intensity) is spread over a wider region. Therefore, decreasing brightness.

 

[Hateexams93]

http://www.xtremepapers.me/CIE/Internat ... 4_qp_2.pdf Q number 1 (b) what exactly do we have to draw? i tried triangle , i got the wrong answer , and how d we know which force is 8 N and which one is 6N???????

 

[sasukeuchiha]

they didn't ask for the direction so doing it either way will give the right answer.
draw a 6N force on one line and 8N force on the other. Draw 2 same parallel forces to complete the parallelogram
and draw the resultant from where the tails meet to where the heads of the arrows representing forces meet. Measure it.
remember to mention the scale too.

 

[AlyHamza]

why the brightness decreases when the wavelenght increases ?????????????????????????????

It doesn't! It only increases if you increase intensity or increase the separation of the slits! Or use a brighter light

v=fλ so f= v/λ . λ is increased, so f is decreased. Use Intensity is directly proportional to (frequency)^2 also. Intensity is decrease, brightness is decreased.

Also boz increasing the wavelength means fringe separation (x) has increased so for wider fringes the energy of light wave is redistributed. the same energy which was illuminating a smaller area is now illuminating a larger area so the fringes will be less bright.

Note: u wud be thinking that intensity is directly proportional to (amplitude)^2......... yes it is...... but it is also to (frequency)^2.

Hope this clears all ur misconceptions.........

 

[AlyHamza]

oohhh i got the answer nm )

So what effect does increasing slit separation have on the brightness of fringes????