Problem about calculating focal length of a telescope

In summary, the person is preparing for an optics exam and is having trouble understanding a formula on the second page. They are specifically asking for help with the last step, where they are confused about how the coefficient -(1+b) was obtained. They understand the substitutions made but are getting a different sign in the second term and want to see all the steps.
  • #1
Blacky&Imy
3
0
Hello!
I am preparing an exam about optics and I can't understand a formula.my problem is at the end of the second page (the explanation is in Italian, but the formulas are easy to read for everybody).
I can't understand how in the last step

f=R/2 - (1+b) * r^2/4R etc they found -(1+b)

can somebody help me please?
 

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  • #2
Are you asking how they mathematically got from the previous equation to the last one?
 
  • #3
yes. I understand what is substituted in what, but I get a different sign in the second term, and I'd like to see all the passages...
 

Related to Problem about calculating focal length of a telescope

1. What is the focal length of a telescope?

The focal length of a telescope is the distance between the primary lens or mirror and the point where the light rays converge to form a sharp image.

2. How is the focal length of a telescope calculated?

The focal length of a telescope can be calculated by dividing the distance from the primary lens or mirror to the focal point by the magnification of the telescope.

3. What factors affect the focal length of a telescope?

The focal length of a telescope can be affected by the size and shape of the primary lens or mirror, the distance between the primary lens or mirror and the focal point, and the magnification of the telescope.

4. Why is knowing the focal length important in telescope design?

Knowing the focal length is important in telescope design because it determines the magnification and field of view of the telescope. It also affects the clarity and sharpness of the images produced by the telescope.

5. How can I measure the focal length of my telescope?

The most accurate way to measure the focal length of a telescope is to use a collimator, which is a device specifically designed for measuring focal length. However, you can also estimate the focal length by using a ruler to measure the distance between the primary lens or mirror and the focal point.

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