Solving Telescope Optics Homework Question Involving Five Lenses

In summary: I don't think so. As you can see in the Google Images, arrows are sometimes used to show when an image is inverted or not.
  • #1
chemphys1
27
0

Homework Statement



*The diagram of the telescope is attached*

Question states

A telescope is constructed from five thin lenses of Diameter D and focal lengths 2F, F, F,F,2F
located at x = 0,2F,4F,6F,8F
Trace the path of a ray entering the system parallel to the optical axis


The Attempt at a Solution



This is undergraduate lab in chemistry but I haven't done physics before, I understand the middle line is the optical axis, but not much more. I've tried to do some reading but nothing seems to relate back to this question as it has little information about the type of lense/telescope and I seem to just be confusing myself completely

Any help really appreciated, quite confused!
 

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  • #2
No tilts uninteresting
 
  • #3
Sorry I don't follow?
 
  • #4
Vespa71 said:
No tilts uninteresting

chemphys1 said:
Sorry I don't follow?

Disregard his reply. He is saying that the problem is fairly easy as stated, but it's an intro course so there is nothing wrong with starting with straightforward questions.

I'll post a reply to your OP in a sec...
 
  • #5
chemphys1 said:

Homework Statement



*The diagram of the telescope is attached*

Question states

A telescope is constructed from five thin lenses of Diameter D and focal lengths 2F, F, F,F,2F
located at x = 0,2F,4F,6F,8F
Trace the path of a ray entering the system parallel to the optical axis


The Attempt at a Solution



This is undergraduate lab in chemistry but I haven't done physics before, I understand the middle line is the optical axis, but not much more. I've tried to do some reading but nothing seems to relate back to this question as it has little information about the type of lense/telescope and I seem to just be confusing myself completely

Any help really appreciated, quite confused!

One Relevant Equation that you should have posted is the "Lens Equation". Can you post it? And show a diagram demonstrating what it means for ray tracing through a single thin lens?
 
  • #6
berkeman said:
One Relevant Equation that you should have posted is the "Lens Equation". Can you post it? And show a diagram demonstrating what it means for ray tracing through a single thin lens?

Ok thanks

Lens equation for a thin lens is 1/f = 1/d1 + 1/d2 ?

where f is the focal length of lens, d1 is image to lens distance, d2 object to lens distance

https://www.google.co.uk/search?q=l...ork-help%2Foptics%2Flens-formula.aspx;254;112

Not too sure about the lens, how do I know if the lens is concave or convex in this question?
 
  • #7
chemphys1 said:
Ok thanks

Lens equation for a thin lens is 1/f = 1/d1 + 1/d2 ?

where f is the focal length of lens, d1 is image to lens distance, d2 object to lens distance

https://www.google.co.uk/search?q=l...ork-help%2Foptics%2Flens-formula.aspx;254;112

Not too sure about the lens, how do I know if the lens is concave or convex in this question?

If the focul length is positive, it is convex (focuses a real image). Are you sure the problem statement is complete, and all of the focul lengths are positive as shown in your OP?
 
  • #9
berkeman said:
If the focul length is positive, it is convex (focuses a real image). Are you sure the problem statement is complete, and all of the focul lengths are positive as shown in your OP?

Yes all the focal lengths are positive,
the only difference between the question and my diagram is the diagram has arrows pointing up and down on the lenses, does that indicate convex too?
 
  • #10
chemphys1 said:
Yes all the focal lengths are positive,
the only difference between the question and my diagram is the diagram has arrows pointing up and down on the lenses, does that indicate convex too?

I don't think so. As you can see in the Google Images, arrows are sometimes used to show when an image is inverted or not. Can you post a scan of the actual problem image?
 
  • #11
attached
 

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  • #12
Oh, double arrows. Yes, that might also imply convex/converging lenses.

So can you draw the first ray, coming in from the left about half-way up the first lens? Where does it cross the centeral axis?
 
  • #13
Like that? crossing at focal point F after the lens?
 

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  • #14
is the whole pathway of the ray this? keeps going back through the next focal point?
 

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  • #15
The first lens has a focul length of 2F, not F.
 
  • #16
berkeman said:
The first lens has a focul length of 2F, not F.

How does that affect the ray, does it not converge to the focal point at 3f?

would it hit the optical axis at 2F on the x axis, through the centre of the 2nd mirror?
 
  • #17
this?
 

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  • #18
chemphys1 said:

Homework Statement



*The diagram of the telescope is attached*

Question states

A telescope is constructed from five thin lenses of Diameter D and focal lengths 2F, F, F,F,2F
located at x = 0,2F,4F,6F,8F
Trace the path of a ray entering the system parallel to the optical axis


The Attempt at a Solution



This is undergraduate lab in chemistry but I haven't done physics before, I understand the middle line is the optical axis, but not much more. I've tried to do some reading but nothing seems to relate back to this question as it has little information about the type of lense/telescope and I seem to just be confusing myself completely

Any help really appreciated, quite confused!

This may help you. Here you can see the ray paths.
convex-lens-ray-real.gif


http://mcat-review.org/light-geometrical-optics.php
 
  • #19
Sorry thank you for all the help but I'm really not understanding

The question says trace a ray, will I have 1 line like I did in my diagram or 3 lines like these images?
I literally knew nothing on optics before this question and my google searches were getting me more confused, including all these diagrams with lines going everywhere, multiple focal points etc.

Is my attempted diagrams completely wrong?
 
  • #20
chemphys1 said:
Sorry thank you for all the help but I'm really not understanding

The question says trace a ray, will I have 1 line like I did in my diagram or 3 lines like these images?
I literally knew nothing on optics before this question and my google searches were getting me more confused, including all these diagrams with lines going everywhere, multiple focal points etc.

Is my attempted diagrams completely wrong?

That is your problem statement:

Trace the path of a ray entering the system parallel to the optical axis

So you have to trace only the parallel ray, but you will need all 3 cases to draw it to the end.
 
  • #21
berkeman said:
The first lens has a focul length of 2F, not F.
chemphys1 said:
would it hit the optical axis at 2F on the x axis, through the centre of the 2nd mirror?
Yes. But in the figure you posted, it did not do that.

chemphys1 said:
Is my attempted diagrams completely wrong?
You just need 1 ray, as you have been doing. You started correctly with the parallel-to-the-axis ray, but things went wrong after the 1st lens -- hopefully what I posted above helps with that.
 

1. How do I approach solving a telescope optics homework question involving five lenses?

To solve a telescope optics homework question involving five lenses, it is important to first understand the basic principles of optics and how lenses work. This includes knowing the focal lengths, magnification, and image formation of each lens. Then, carefully read and analyze the given question, breaking it down into smaller parts if necessary. Finally, use the appropriate equations and formulas to calculate the final answer.

2. What are the most common mistakes made when solving telescope optics homework questions?

One of the most common mistakes made when solving telescope optics homework questions is not understanding the given question properly. It is important to carefully read the question and identify what information is given and what is being asked. Another mistake is not using the correct equations and formulas, leading to incorrect calculations. It is also important to double-check all calculations and units to avoid errors.

3. How do I determine the magnification of a telescope with five lenses?

The magnification of a telescope with five lenses can be determined by multiplying the individual magnifications of each lens. The magnification of a single lens is equal to the ratio of the image distance to the object distance. Therefore, to find the magnification of a telescope with five lenses, simply multiply the magnifications of each lens together.

4. What are the different types of aberrations that can occur in a telescope with five lenses?

The different types of aberrations that can occur in a telescope with five lenses include chromatic aberration, spherical aberration, coma, astigmatism, and distortion. Chromatic aberration is the most common and occurs when different wavelengths of light are focused at different points, resulting in a blurred image. Spherical aberration occurs when the edges and center of the lens do not focus light at the same point. Coma, astigmatism, and distortion are also types of image blurring caused by imperfections in the lenses.

5. How can I check my solution to a telescope optics homework question involving five lenses?

To check your solution to a telescope optics homework question involving five lenses, you can use the back-substitution method. This involves substituting your calculated values back into the original equations to see if they satisfy the given conditions. You can also double-check your calculations and units, as well as compare your answer to the expected result. Additionally, seeking assistance from a teacher or peer can help verify the accuracy of your solution.

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