focal

  1. S

    Focal lenses

    What are focal lenses?
  2. N

    Basic question about primary mirror and focal length

    I have a Cassini PM-160 spherical mirror used in telescopes as the primary mirror. The mirror is concave with a radius of curvature of 2600mm and focal length of 1300mm. I am using the mirror in an imaging application. I have a very basic question. If an on object is located beyond the focal...
  3. N

    How far from focal length of a lens does the nearest infinity begin

    Q. How can we make out whether the the object is beyond C or infinity? Q. At what nearest distance does infinity start from,from the focus(focus Of any lens or mirror)? Means is there any relation between the point from where infinity starts and the focal length or curvature of any lens or...
  4. P

    The effect of focal length on collimated light output

    I was trying to get an idea of what effect if any different focal lengths for the same diameter lens had on a collimated beam? The conclusion I have come to so far is that it has no effect on the final collimated output, only the distance the light source must be from the lens in order to...
  5. K

    problematic spherical mirror focal spot

    hello guys, i monitor with a pixeled camera the focal spot from a spherical mirror but i don't get a nice (even nearly)sperical spot but something weird that shows interference. I woul appreciate a little help. Here are the data (i will make it short, in case anyone can help and need more info i...
  6. A

    Optics / focal length

    I am having a very hard time figuring out this problem and was hoping I could get some help. Problem: What was the focal length when the radius of curvature was 0.70m and index of refraction was 1.8? I believe the formula is the Lens markers equation 1/f=(n-1)1/R but I would need to solve...
  7. J

    A diverging lens has a focal length of...

    a) A diverging lens has a focal length of 19.3cm. An object 1.14 cm in height is placed 324cm in front of the lens. Locate the position of the image. Answer in units of cm. b) What is the magnification? c) Find the height of the image. Answer in units of cm.
  8. A

    Finding focal length

    Used as a magnifying glass, the image of an object 4cm from a converging lens is five times the object length. What is the focal length of the lens? I used m=v/u=5 v=4*5=20cm the i used 1/v+1/u=1/f 1/20+1/4=1/f f=3.33cm the problem is here, the image is supposed to be same way up and virtual...
  9. G

    Focal Length...

    Got some work from my dad, but one question kinda stumped me. A short sighted person can view an object clearly only when it is between 11 cm and 19 cm from her eyes. Calculate: 1. The Focal Length of the specatacles required to give her a near point of 25 cm. I don't know what equation to use...
  10. I

    "The Music" (angles, focal length, lenses, etc.) URGENT

    The well known 17th Century Dutch painter Johannes Vermeer only painted 30 paintings during his life. However, they were created with incredible, almost photographic-like detail. The use of perspective was ahead of his time. Recently, many have come to wonder how Vermeer created such...