If I was designing a telecope where the focal lengths of the lenses were 400 mm and 50 mm, how much space would I need between the lenses to make it work properly? Is there a mathermatical equation to arrive at this answer?
Thanks!
2007-07-27 00:54:26 · 6 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
um Starry-eyed, I don't believe that is correct. There must be a specific amount of space between the focal lengths of the lenses. It is not simply adding the two focal lengths together.
2007-07-27 01:18:32 · update #1
450 mm.
The focal length of the primary + the focal length of the eyepiece.
2007-07-27 01:15:10 · answer #1 · answered by Owl Eye 5 · 2⤊ 0⤋
You really do just add them. To make a clear image the focal point of the eyepiece must be at the same place as the focal point of the objective. The objective makes an image at its focus 400mm from it and the eyepiece must be 50mm from that image to make a clear image for your eye when you look through the eyepiece. This assumes the object you are looking at is infinitely far away, which for practical purposes i anything over a mile or so. To focus closer, there is a formula you need to use to calculate where to put the eyepiece. Basically, the closer the object the farther from the objective the image will appear. The extreme case would be looking at an object 400 mm away, in which case the image would be infinitely far away. The middle case is an object 800mm away makes an image 800mm from the lens.
2007-07-27 10:00:11 · answer #2 · answered by campbelp2002 7 · 2⤊ 0⤋
Simply adding the focal lengths is approximately correct. Because your eye has some capacity to adjust focus, the focus of the objective does not have to be placed precisely at the focus of the eyepiece. The focus knob changes the spacing between these two lenses some small amount.
2007-07-27 18:41:13 · answer #3 · answered by Mr. Quark 5 · 0⤊ 0⤋
No, really, 450 mm is correct. The primary lens takes the parallel rays coming from infinity, and focuses them to an image that is 400 mm behind. The eyepiece lens then takes that image and magnifies it, converting it back to a parallel bundle of rays, but smaller.
To focus closer than infinity, the two lenses need to be slightly further apart, by an amount given by the "thin lens formula".
2007-07-27 08:29:55 · answer #4 · answered by cosmo 7 · 2⤊ 0⤋
It depends on the focus of the Lin's ,but the greater focal length the better resolution.
2007-07-27 09:01:51 · answer #5 · answered by JOHNNIE B 7 · 0⤊ 1⤋
400mm IS your focal length or length between the lenses.
The distance between the 50mm front objective and the back eyepiece or resolving lense is 400mm
2007-07-27 09:18:35 · answer #6 · answered by Anonymous · 0⤊ 1⤋