Understanding the Role of Convex Lenses in Fraunhofer Diffraction

Click For Summary
The discussion centers on the behavior of light rays passing through convex lenses in the context of Fraunhofer diffraction. A monochromatic light source is placed at the principal focus of a convex lens, creating a parallel beam that encounters a narrow slit. Participants express confusion regarding the role of a second convex lens, with some perceiving it as diverging the rays instead of converging them. Clarifications indicate that the rays are indeed converging after passing through the lens, aligning with standard optical principles. The conversation highlights the importance of understanding lens behavior in diffraction experiments.
Prashasti
Messages
63
Reaction score
2

Homework Statement


A monochromatic source of light 'S' is placed at the principal focus of a convex lens 'L1'. A parallel beam of light or a plane wave front is incident on the narrow slit represented by AB (its width - 'a')

Homework Equations


So, what my teacher did was,
She showed diffraction of the light rays as they pass through the slit.
And then she made the rays to meet at a point 'P'.
Look at the image. Doesn't the convex lens L2 seem to be actually 'diverging' the rays? Shouldn't it 'converge' them?
I'm literally confused about it, because all the books seem to support my teacher.
singleslitexpt.png
 
Physics news on Phys.org
Prashasti said:
Doesn't the convex lens L2 seem to be actually 'diverging' the rays? Shouldn't it 'converge' them?
Looks like it's converging to me. In this image, the left lens is converging and the right lens is diverging.

foclen.gif

Image compliments of http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/foclen.html
 
  • Like
Likes Prashasti
Yes the parallel rays are converging. They were parallel and are now drawing together.
 
Does it mean why my teacher did was wrong?
 
Jilang said:
Yes the parallel rays are converging. They were parallel and are now drawing together.
I 'm talking about the second lens...
 

Thread 'Magnitude of buoyant force in fluids of different densities'

The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?
View full post »

Similar threads

Fraunhofer Diffraction Pattern Ratio of Power Densities
  • · Replies 34 ·
2
Replies
34
Views
3K
How Does the Fraunhofer Condition Affect Diffraction Patterns?
  • · Replies 11 ·
Replies
11
Views
2K
[Optics] Find maximum order number, Fraunhofer diffraction
  • · Replies 7 ·
Replies
7
Views
2K
Understanding Two Convex Lenses: Ray Diagram and Focal Lengths
  • · Replies 3 ·
Replies
3
Views
2K
Treating Oblique Incidence as a Fraunhofer Diffraction Problem
  • · Replies 1 ·
Replies
1
Views
2K
Double slits and convex lens interference
  • · Replies 8 ·
Replies
8
Views
3K
Graduate Fourier optics model of a 4f system
  • · Replies 1 ·
Replies
1
Views
3K
Undergrad Using Diffraction (i.e., Fresnel Zone Plate) to defocus/diverge light
  • · Replies 2 ·
Replies
2
Views
2K
5 Questions dealing with Optics, image included
  • · Replies 1 ·
Replies
1
Views
3K
Emergent light produced by two lenses
  • · Replies 15 ·
Replies
15
Views
2K