Help with understanding Young's Derivation

  • Thread starter Thread starter aeromat
  • Start date Start date
  • Tags Tags
    Derivation
AI Thread Summary
In Young's derivation, the confusion arises from the approximation that S1P is nearly parallel to BP when the distance L is much greater than y. This assumption allows for the simplification that S1P and BP can be treated as equal in length, which is crucial for deriving the equation. Although parallel lines do not intersect, in this context, they are close enough to parallel that the approximation holds without significant error. As L increases relative to y, the triangle formed becomes thinner, enhancing the validity of this approximation. Understanding this concept is key to grasping the logic behind Young's experiment.
aeromat
Messages
113
Reaction score
0

Homework Statement


Here they are deriving the equation for Young's experiment: http://www.physicsclassroom.com/Class/light/U12L3c.cfm

The part where they start bringing up "Assertion" and "Logic/Rationale" is where I got confused:
They mention for part ii) that if the distance L >>> y, then S1P is || (parallel) to BP.
u12l3c3.gif

iii

S1P = BP

If S1P and BP are || and line S1B is perpendicular to BP, then the length BP = length S1P.
If they are parallel to each other, wouldn't the two lines NOT connect together to form a triangle? What I know about parallel lines, they never intersect, and in this case, they are intersecting at P. :confused:

Homework Equations



Young's Equation for a double slit experiment
 
Physics news on Phys.org
They're not actually parallel, they're just close enough to parallel that you can pretend that they are parallel (without significant loss of accuracy). It's an approximation. The larger you make L in comparison to y, the "thinner" the triangle gets, and the better this approximation is.
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Confusion Calculating Young's Modulus
Replies
5
Views
2K
Putting a slab of some material just after the slits in Young's model
Replies
14
Views
2K
Thomas Young's double slit experiment
Replies
6
Views
4K
Young's Double Slit - Low intensity
Replies
1
Views
1K
Young's Two Slit Experiment Question
Replies
2
Views
2K
Requirements for an observable pattern in young's experiment
Replies
2
Views
934
Young's double-slit interference?
Replies
4
Views
5K
Archived Optics: Shift in y from a thin pane of glass, young's experiment.
Replies
1
Views
4K
Understanding the Derivation of Relativistic Mass in Inelastic Collisions
Replies
2
Views
2K
Young's Double Slit Experiment refraction
Replies
7
Views
6K

Hot Threads

Recent Insights

Back
Top