What is the focal point of a lens in a geometrical optics problem?

AI Thread Summary
The discussion focuses on understanding the focal point of a lens in geometric optics. The initial assumption is that the focal point is -25.5 cm, but clarification is sought regarding the relevance of lens radii and refractive index. A suggested approach involves treating the lens's first surface as a mirror to deduce the focal length using the formula f=R/2. This method allows for the calculation of the radius of curvature and ultimately the system's focal length. The conversation concludes with acknowledgment of the guidance provided.
Marioweee
Messages
18
Reaction score
5
Homework Statement
We have a divergent lens on which a beam of parallel rays strikes from left to right. Part of the light reflects off the first face and the reflected rays converge at the point indicated by the arrow, which is - 25.5 cm from the vertex of the first lens surface. Assuming that the lens is symmetrical, that is, that "R1= -R2 &, which is thin, and whose refractive index is 1.5, state the value of the focal point of the lens with its sign.
Relevant Equations
---
I have recently started with geometric optics and I do not quite understand what this problem asks of me. According to the statement, the focal point of the lens would be -25.5cm, right? That is, it is only a problem of concepts where it is not necessary to take into account the radii of the lenses or the refractive index, right?
Maybe I am very wrong that is why I ask for some help.
This is the picture of the problem that I have done.
WhatsApp Image 2021-10-03 at 20.02.34.jpeg
 
Physics news on Phys.org
Marioweee said:
According to the statement, the focal point of the lens would be -25.5cm, right?
Why would you think that? Hint: Solve the problem in two steps. Step one: Treat the first surface of the lens as a mirror. What can you then deduce?
 
If the first surface is treated as a spherical mirror then f=R/2. From this equation we can determine the value of R1. Then, from the Lensmarker's equation I could determine the focal length of the system, right?
 
Marioweee said:
If the first surface is treated as a spherical mirror then f=R/2. From this equation we can determine the value of R1. Then, from the Lensmarker's equation I could determine the focal length of the system, right?
Right!
 
Thank you very much for your help
 
Thread 'Collision of a bullet on a rod-string system: query'

Thread 'Collision of a bullet on a rod-string system: query'

In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
View full post »

Similar threads

Calculate a radius of a circle on a screen
Replies
3
Views
1K
Inserting thick lenses into a thin lens system and deducing values
Replies
1
Views
2K
Focal length of the eyepiece lens in a compound microscope
Replies
7
Views
1K
Calculate the focal distance of the duplicate
Replies
3
Views
1K
Biconvex Lens Floating on Mercury
Replies
13
Views
3K
Geometric optics: Thin lense equation
Replies
3
Views
2K
A When should I analyze optical problems using ray tracing vs. wavefront analysis?
Replies
12
Views
313
Position of the object and image in this optics problem
Replies
10
Views
2K
Combination lens equation questions
Replies
2
Views
1K
Is the Solution for Rotation of Spherical Mirrors Incorrect?
Replies
16
Views
1K

Hot Threads

Recent Insights

Back
Top