IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: nid404 on March 25, 2010, 05:51:59 pm

Title: URGENT HELP IN PHYSICS!!! REALLY URGENT!!
Post by: nid404 on March 25, 2010, 05:51:59 pm

 A parallel beam of light of wavelength 450 nm falls normally on a diffraction grating which has 300 lines/mm

What is the total number of transmitted maxima?

Ans:15

Please explain it

Thanks in advance...This is really very urgent

Title: Re: URGENT HELP IN PHYSICS!!! REALLY URGENT!!
Post by: astarmathsandphysics on March 25, 2010, 06:21:03 pm

2 hours

Title: Re: URGENT HELP IN PHYSICS!!! REALLY URGENT!!
Post by: nid404 on March 25, 2010, 06:22:08 pm

Ok.. :(

Somebody else could give it a try...please :'(....I'm not too good at waves!

Title: Re: URGENT HELP IN PHYSICS!!! REALLY URGENT!!
Post by: astarmathsandphysics on March 25, 2010, 08:52:34 pm

sin x=nw/d<1
300 line/mm so d=0.001/300=3.33*10^-6
n<d/w=3.33*10^-6/(450*10^-9)=7.4 so n=7
that means 7 fringes on either side +1 in the middle =15 fringes

Title: Re: URGENT HELP IN PHYSICS!!! REALLY URGENT!!
Post by: nid404 on March 26, 2010, 06:00:06 am

Ohhhh......either side of the central maxima!! slipped outta my mind...
luckily i didn't have a question on this

Thanks sir