Can you have an anti focal point of a lens?

  • Context: Graduate 
  • Thread starter Thread starter johne1618
  • Start date Start date
  • Tags Tags
    Focal Lens Point
Click For Summary
SUMMARY

The discussion centers on the concept of an "anti" focal point in a convergent lens system, specifically regarding light cancellation at the focal point. John proposes the idea of using concentric rings made of glass with varying refractive indices to achieve light cancellation by ensuring that light waves arrive at the focal point out of phase. The conversation also explores the implications of placing an absorbing sheet at this anti-focal point, questioning whether photons could "tunnel" through it due to the zero probability of detection at that location.

PREREQUISITES
  • Understanding of convergent lens principles
  • Knowledge of light wave interference and phase cancellation
  • Familiarity with refractive index concepts
  • Basic principles of quantum tunneling
NEXT STEPS
  • Research the design and effects of concentric ring lenses
  • Explore the principles of wave interference in optics
  • Study the implications of quantum tunneling in photon behavior
  • Investigate advanced lens designs for light manipulation
USEFUL FOR

Optics researchers, physicists, and engineers interested in advanced lens design and light manipulation techniques.

johne1618
Messages
368
Reaction score
0
Can you have an "anti" focal point of a lens?

Hi,

Imagine putting a convergent lens in the path of a laser beam. I put a small light meter at the focal point of the lens.

If I move the lens along the beam will there be positions of the lens where the light paths through it completely cancel at the focal point so that no photons are detected there?

John
 
Science news on Phys.org


Hi,

I've been thinking...

In order to get the effect of light cancellation at a focal point maybe one needs to implant concentric rings inside the lens made of glass with a different refractive index. Adjacent rings could then be designed to cause the light to arrive at the focal point precisely out of phase.

Maybe that would do it?
 
Last edited:


If you could make a lens that focussed light to an "anti" focal point what happens if you place a thin absorbing sheet at that point?

Would light somehow "tunnel" through the sheet as photons cannot be absorbed at the anti-focal point (zero probability for them to be detected there)?
 

Similar threads

Graduate Diffraction pattern due to a lens with focal length f
  • · Replies 2 ·
Replies
2
Views
1K
Undergrad How to calculate focal length?
  • · Replies 8 ·
Replies
8
Views
3K
Undergrad How Can I Build an Effective DIY Helmet-Mounted HUD?
  • · Replies 19 ·
Replies
19
Views
6K
Graduate Thought experiments suggest problem with published work
  • · Replies 8 ·
Replies
8
Views
2K
Undergrad Digital Micromirror Device based optical setup
  • · Replies 7 ·
Replies
7
Views
3K
Undergrad Collimating a laser beam with a fixed focal point?
  • · Replies 9 ·
Replies
9
Views
4K
Undergrad Principal plane of a thin lens
  • · Replies 8 ·
Replies
8
Views
3K
Graduate How to model converging illumination through object plane (in ZEMAX)
  • · Replies 1 ·
Replies
1
Views
1K
Undergrad Combing Lasers To Create One Mega Laser
  • · Replies 10 ·
Replies
10
Views
3K
Undergrad Focal length of 2 lenses to reduce laser beam diameter
  • · Replies 2 ·
Replies
2
Views
6K