You are Here: Home >< Physics

# Central fringe physics !!

Announcements Posted on
Would YOU be put off a uni with a high crime rate? First 50 to have their say get a £5 Amazon voucher! 27-10-2016
1. A narrow beam of light is directed normally at a slit.
a) blue filter placed in the path of a beam before it reaches the slit. distance across 5 fringes including the central fringe = 18mm find the width of the central fringe
2. Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.

You can also find the Exam Thread list for A-levels here and GCSE here.

Just quoting in Puddles the Monkey so she can move the thread if needed
Spoiler:
Show
(Original post by Puddles the Monkey)
x
3. Thanks
4. (Original post by ashg99)
A narrow beam of light is directed normally at a slit.
a) blue filter placed in the path of a beam before it reaches the slit. distance across 5 fringes including the central fringe = 18mm find the width of the central fringe
The central fringe is double the width of the other fringes, so we can take the total width of 5 fringes including the central fringe to be equal to 6 "outside fringes"

18/6 = width of subsidiary fringes = 3mm

because central fringe = 2xsubsidary fringes
= 2*3 = 6mm

If you then add 3+3+6+3+3 (the widths of all the fringes in order, the answer = 18mm, so central fringe = 6mm

(I hope this makes sense, it did to me haha)
5. (Original post by jakepds)
The central fringe is double the width of the other fringes, so we can take the total width of 5 fringes including the central fringe to be equal to 6 "outside fringes"

18/6 = width of subsidiary fringes = 3mm

because central fringe = 2xsubsidary fringes
= 2*3 = 6mm

If you then add 3+3+6+3+3 (the widths of all the fringes in order, the answer = 18mm, so central fringe = 6mm

(I hope this makes sense, it did to me haha)
Thanks mate it did make sense. LoL

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: April 4, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### University open days

Is it worth going? Find out here