Physics HL Question

littlneutralone

Can anyone help me with 2005, Q7 on light, lasers and slits and patterns on screens...

(iii) What is the effect on the pattern when-
the wavelength of the light is increased?

Marking scheme says the pattern spreads out more, but I can't get my head around it because..if you increase the wavelength, then more diffraction occurs, right? (probably wrong ha) And more diffraction = more interference = more lines....

That's really bad reasoning.

If anyone can explain this to me thanks in advance

Cokehead Mother

nlambda = dSinA

sinA = nlambda/d

If lambda increases, then sinA increases so the light spreads out more. (because as sinA gets larger, so does A)

dshalloo

Also on the topic of light, does anybody have the derivation for

n(lambda)=dSin(theta)

Please

The Walsho

Thanks to Cokehead Mother on another thread for this : http://www.studentxpress.ie/proof1.pdf

littlneutralone

Cokehead Mother wrote: »

nlambda = dSinA

sinA = nlambda/d

If lambda increases, then sinA increases so the light spreads out more. (because as sinA gets larger, so does A)

THANK YOU. Wow I'm going to fail with flying colours.

Peleus

is it possible to get away with not doing monochromatic light and defraction gratings etc because i HATE that sh1t! and also a long question on sound (i'll be doing the sound experiments obv)?? I want an A so i dont want to waste time studying that stuff cos i hate it. Do you think i'll be ok with basic light, basic sound, mechanics, electricity, magnetism, modern physics and particle physics?

declan_lgs

littlneutralone wrote: »

THANK YOU. Wow I'm going to fail with flying colours.

No, you're going to pass with d over lambda colours.

Oh I tried

dshalloo

The Walsho wrote: »

Thanks to Cokehead Mother on another thread for this : http://www.studentxpress.ie/proof1.pdf

Thank you :D

A-Bit-Dodge

Hhaha little neutral one... brilliant name altogether!!

littlneutralone

In honour of the only section of physics I can stomach.


If any physical people are still up...could anyone explain why -
in 2002, Q8, (ii) why you use W=IV to solve it? Why can't you use P=(I^2)R? [I know you use the second formula for part (iii) but what's the difference?]

declan_lgs wrote: »

No, you're going to pass with d over lambda colours.



Oh I tried

You did good man, with what you had :pac:

Peleus

littlneutralone wrote: »

In honour of the only section of physics I can stomach.


If any physical people are still up...could anyone explain why -
in 2002, Q8, (ii) why you use W=IV to solve it? Why can't you use P=(I^2)R? [I know you use the second formula for part (iii) but what's the difference?]


You did good man, with what you had :pac:

Ye, thats a tricky one... emmm, p=I^2R gives the rate at which heat is produced in conductor. and P=IV says that the Power Rating = the current through the curcuit x the voltage across.

If ever they ask for heat/energy produced in circuit use P=I^2R (joules law). and if they say it has a power of xyz then use the P=IV formula. Safest bet. good luck tomorow!

littlneutralone

So...P=IV is kinda focused on the powerful-driving-current aspect, and P=I^2R is more for heat losses and other zany conversions?


Thanks and good luck to you too!

Peleus

ye, if you keep that in mind you should know which one to use.