Question regarding a two-lens system

  • Thread starter Thread starter pisquared
  • Start date Start date
  • Tags Tags
    Optics System
Click For Summary
SUMMARY

The discussion revolves around a two-lens optical system consisting of two converging lenses, each with a focal length of 15 cm, positioned 20 cm apart. An object is placed 30 cm in front of the first lens. The final image is formed 10 cm behind the second lens, and the total magnification is calculated using the formula Mtot = M1 * M2. Participants clarify that the image formed by the first lens serves as the object for the second lens, emphasizing the importance of treating the object distance for the second lens as negative since the image is located behind it.

PREREQUISITES
  • Understanding of lens formulas, specifically (1/f) = 1/do + 1/di
  • Knowledge of magnification calculations using Mtot = M1 * M2
  • Familiarity with ray diagrams for optical systems
  • Basic principles of converging lenses and image formation
NEXT STEPS
  • Study the derivation and application of the lens formula (1/f) = 1/do + 1/di
  • Explore advanced topics in optical systems, such as multi-lens systems and their combined effects
  • Learn about the significance of sign conventions in optics, particularly for object and image distances
  • Investigate practical applications of converging lenses in devices like cameras and microscopes
USEFUL FOR

Students studying optics, physics educators, and anyone interested in understanding the behavior of multi-lens systems in image formation and magnification.

pisquared
Messages
2
Reaction score
0

Homework Statement


Two converging lenses, each of focal length 15 cm, are placed 20 cm apart, and an object is placed 30 cm in front of the first. Where is the final image formed and what is the magnification of the system?

Homework Equations


Mtot = M1 * M2
(1/f) = 1/do + 1/di

The Attempt at a Solution


[/B]
Okay, I was able to find the image distance would be 30 cm, but I have no idea how that would happen if the lenses are 20 cm apart. When drawing the ray diagram, the rays touch the second lens before converging, so I don't know where to go from there. Any help would be appreciated. Thanks!
 
Physics news on Phys.org
pisquared said:

Homework Statement


Two converging lenses, each of focal length 15 cm, are placed 20 cm apart, and an object is placed 30 cm in front of the first. Where is the final image formed and what is the magnification of the system?

Homework Equations


Mtot = M1 * M2
(1/f) = 1/do + 1/di

The Attempt at a Solution


[/B]
Okay, I was able to find the image distance would be 30 cm, but I have no idea how that would happen if the lenses are 20 cm apart. When drawing the ray diagram, the rays touch the second lens before converging, so I don't know where to go from there. Any help would be appreciated. Thanks!
One way is to take the image that would be formed by the first lens and treat it as the source object for the second lens. You just have to be careful about which side the final image will be.
 
  • Like
Likes pisquared
pisquared said:
Okay, I was able to find the image distance would be 30 cm, but I have no idea how that would happen if the lenses are 20 cm apart. When drawing the ray diagram, the rays touch the second lens before converging, so I don't know where to go from there.
You can take that image as object of the second lens. As it is behind the second lens, take the object distance negative.
 
  • Like
Likes pisquared
@ehild @haruspex So the first image would go straight through the second lens and be 10 cm behind it, then be the object of the second lens?
 
pisquared said:
@ehild @haruspex So the first image would go straight through the second lens and be 10 cm behind it, then be the object of the second lens?
Yes.
 

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

Analyzing this 2-lens optical system
  • · Replies 5 ·
Replies
5
Views
2K
Inserting thick lenses into a thin lens system and deducing values
  • · Replies 1 ·
Replies
1
Views
2K
Focal length of the eyepiece lens in a compound microscope
  • · Replies 7 ·
Replies
7
Views
2K
Find the location and length of the final image
  • · Replies 2 ·
Replies
2
Views
1K
Calculating Chromatic Aberration
  • · Replies 2 ·
Replies
2
Views
2K
Multiple reflections in a mirror system
  • · Replies 5 ·
Replies
5
Views
495
Optics Problem with a Double Lens System
  • · Replies 1 ·
Replies
1
Views
2K
Calculate a radius of a circle on a screen
  • · Replies 3 ·
Replies
3
Views
1K
Compound Microscope: Calculating Image Location with Two Lenses
  • · Replies 4 ·
Replies
4
Views
2K
Understanding a Converging Lens and Its Two Positions
  • · Replies 3 ·
Replies
3
Views
2K