Question

I am having trouble understanding the relationship between slit width, slit spacing and wavelength with the pattern of waves on the screen.

What does it mean for a slit width to be greater/less than the wavelength of light?

What does it mean for the spacing between two slits being larger/less than the slit width?

Here's an example of a problem I can't figure out:

In a two-slit interference pattern, a minimum between the m = 3 and m = 4 maxima occurs because:

A. One of the slits is 3lambda farther than the other to this point

B. One of the slits is 3.5lambda closer than the other to this point

C. One of the slits is 4lambda closer than the other to this point

D. The waves from the two slits arrive with one-quarter wave phase difference

E. The waves from the two slits arrive with identical phase

Not interested in an answer, just an explanation!

Answer 1

People commonly use slit width to represent the distance between two slits in YDSE

But slit width represents the widness of the slit

slit spacing is centre to centre distance between two slit, we usually use this term in diffracting grating problems

  

For the given question I think b should be correct as for destructive interference (minima) the path diferrence between two light must be of the form (2n+1)K/2 ,where K is wavelength of light used 3.5 comes when n=3

and it lies between 3 and 4