- #1
Von Neumann
- 101
- 4
Question:
I'm sure this is a stupid question, but it has been bothering me lately so I'll ask it anyhow.
In Young's Two Slit experiment the conditions for max and min are
[itex]dsin\theta=m\lambda[/itex] (max)
[itex]dsin\theta=(m+\frac{1}{2})\lambda[/itex] (min)
where m is an integer and d is the separation of the slits and [itex]\theta[/itex] is the angle the lower ray makes with the horizontal.
If the separation d of the slits is much smaller than the distance between the slits and a screen (on which they meet at point), these equations are said to be exact.
However, and this is what confuses me, if parallel light rays are used, the path difference is [itex]dsin\theta[/itex] even if D is not much larger than d. (ie. placing the screen at the focal plane of a converging lens.) If the light rays are parallel, how could they ever focus at a point on the screen? By definition parallel lines never intersect.
I'm obviously misunderstanding something monumental, so I apologize in advance.
I'm sure this is a stupid question, but it has been bothering me lately so I'll ask it anyhow.
In Young's Two Slit experiment the conditions for max and min are
[itex]dsin\theta=m\lambda[/itex] (max)
[itex]dsin\theta=(m+\frac{1}{2})\lambda[/itex] (min)
where m is an integer and d is the separation of the slits and [itex]\theta[/itex] is the angle the lower ray makes with the horizontal.
If the separation d of the slits is much smaller than the distance between the slits and a screen (on which they meet at point), these equations are said to be exact.
However, and this is what confuses me, if parallel light rays are used, the path difference is [itex]dsin\theta[/itex] even if D is not much larger than d. (ie. placing the screen at the focal plane of a converging lens.) If the light rays are parallel, how could they ever focus at a point on the screen? By definition parallel lines never intersect.
I'm obviously misunderstanding something monumental, so I apologize in advance.