How does the power of a lens affect its ability to focus light?

Click For Summary

Discussion Overview

The discussion revolves around the relationship between the power of a lens and its ability to focus light, particularly in the context of experiments using bottles filled with various liquids. Participants explore concepts related to focal length, intensity of light, and the implications of the inverse square law.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant observes that denser liquids with higher refractive indices lower the focal length and increase lens power, resulting in faster burning of paper placed at the focal point.
  • Another participant explains that a shorter focal length corresponds to greater optical power, which bends light rays more strongly.
  • Some participants question how focal length affects the convergence of light, particularly whether focusing light at a closer distance results in more light being focused than at a farther distance.
  • There is a discussion about the inverse square law, with some arguing it does not apply in this context, while others assert that it is relevant for light that diverges in a spherical wavefront.
  • A later reply suggests that light cannot be focused to a single point, and the size of the focal spot varies with different lens powers due to interference effects in the wavefront.
  • Participants also debate the relevance of laser light and its adherence to the inverse square law, with differing views on how it behaves at long distances.
  • Some participants express frustration with the focus on teaching methods rather than the physics concepts at hand.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the applicability of the inverse square law in this context, nor on the implications of focal length on light convergence. Multiple competing views remain regarding the behavior of light and the interpretation of experimental results.

Contextual Notes

Some limitations in the discussion include the crude nature of the lenses used in experiments, which may affect the clarity of observations and conclusions drawn. Additionally, there are unresolved questions regarding the mathematical and physical principles involved in focusing light.

  • #31
Well then my guess was wrong, but I'm not surprised.
 
Science news on Phys.org
  • #32
Well, you're correct in that you need to take the aberrations into account to determine how well the image is focused at the focal plane, which will affect how fast the OP burns through paper.
 
  • #33
Meron35 said:
So I've been doing some experiments, using bottles filled with various liquids and timing how long they take to burn paper which is placed at the focal point (where the light was focused).
This is an interesting investigation---is it something you thought up, or is it in a science program you are studying at school?
 

Similar threads

Undergrad Lens Calculations to Focus Light
  • · Replies 10 ·
Replies
10
Views
4K
Undergrad Focusing UV light from a 275nm LED down to a small spot
  • · Replies 10 ·
Replies
10
Views
3K
Undergrad How to couple light from a very small source into spectrometer?
  • · Replies 10 ·
Replies
10
Views
2K
Undergrad Prism Spectrometer Objective: Optics Question
  • · Replies 9 ·
Replies
9
Views
3K
Undergrad Condenser lens retrofit for a lighting application
  • · Replies 24 ·
Replies
24
Views
3K
Graduate Determining the light intensity in a double convex lens
  • · Replies 7 ·
Replies
7
Views
4K
Undergrad Does focusing light with a lens create a light gradient?
  • · Replies 4 ·
Replies
4
Views
2K
Graduate Can a Convex Lens Converge a Tilted Wavefront?
  • · Replies 2 ·
Replies
2
Views
2K
Graduate Optics: Concentrating light with a lens
  • · Replies 7 ·
Replies
7
Views
4K
Undergrad What is the relationship between numerical aperture and resolution in lenses?
  • · Replies 1 ·
Replies
1
Views
2K