My teacher goes through this physics work so quick, we're into the 2nd day of "The nature of the wavelength and Im completely lost.

Nobody understands it, and neither do I!

The things I do not understand:

What are nodal points? Is this where the trough and crest meet? When they say that 2 nodal points are say, 6cm apart, does that mean they are completely beside eachother, or can they be anywhere?

What is S1,S2, etc.? Is this where the light comes OUT of? Or is this the BEAMS of light? Are these the "slits" the light comes out of? So therefore there could also be an S3.S4 etc meaning more slits??

What is "Xn"? What is this? A length or a point??... What does it connect?

When it says "nodal lines" are these the lines that usually appear "blurry"? Meaning there is a destructive interference??

Lambda is the wavelength, I know this.

Delta d is the distance between S1, and S2, right?

What is the "screen"??

What is L?

When we're trying to find Beda/or Theta, where is that angle? I know that you are supposed to create a new angle because the orginal angle is too small, but i have NO idea where that is, or how you create the new, more clearer angle?

PLEASE HELP!

Sorry if there are so many questions, I just want to understand thoroughly.

Please use pictures if you can! If not, any help is already greatly appreciated!

Please do not use the terms I already don't know to describe other terms I dont know

Thank you so much! :-D