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Focal length is measured in milimeters (mm) -----------------------------------------------------------------
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Which lens always produces an image that is upright?
Concave lens (diverging) produces an upright image that is virtual. Although to create a real upright image would require 2 convex (converging) lens with a distance of their respective focal lengths between them.
Do near objects have a longer focal length?
Focal length is related to the lens. It has nothing to do with how near or far the object is to the lens or objective.
What is secondary focal leangth?
By definition: "The secondary focal point is where rays that are parallel when they enter the lens cross or appear to have crossed."
What two factors determine the type of image formed by lens?
The focal length of the lens and the distance between the lens and the object.
Point at which light rays are converged by a convex lens?
Focus (only at the focal point if the incoming rays are all parallel to the axis).
What lens has an object more than two focal lengths from the lens that will have an inverted message?
it is convex lens ;)
Lenses are engineered to have specific focal lengths Besides the curvature of the two sides of a lens what determines the focal length?
The material that the lens is made from.
How did bifocal got its name?
Two focal lengths in one lens.
How do you find the power of a lens?
The power of a lens is 1/focal length (measured in meters).
What is the formula for light gathering power for telescopes?
For visual observation: Magnification = (Focal Length of Objective Lens) divided by (Focal Length of Eyepiece) (They have to be measured in the same units.) For prime-focus photography: (One focal-length of the Objective Lens on the film) = (one radian in the sky)
How the focal length of a convex lens changes as the sides of the lens become less curved?
Longer focal lengths and less light rays are being bent. :) It's in the book.
An object seen close up through a convex lens looks than it really is?
A convex lens is a mirror whose middle is larger than the top and bottom. A convex lens is more than two focal lengths. It is smaller and inverted between one and two focal lengths.
What does 18-200mm f mean?
That describes a telephoto lens with the lower and upper focal lengths.
What type of lenses are used when photographing people's faces from a distance?
You would ask for a telephoto lens in a shop. Scientifically they are convex lenses with longer focal lengths than a normal lens. A normal lens has a focal length between 21 and 35 mm, whereas the medium telephoto lenses used for portraiture have focal lengths between 70 and 135 mm.
How do you find power of a power?
The power of a lens is 1/focal length (measured in meters).
How does the eyepiece affect the total magnifacation in a telescope?
A telescope consists of two lenses. 1) The main lens which collects the light ( it is relatively bigger that eyepiece). 2) Eye piece , through which we see. Magnification of a telescope depends on the focal length of the eye piece and the main lens. Magnification = Focal length of the main lens / Focal length of the eyepiece . For example : If the focal length of the main lens is 12 units and the focal length of the eyepiece is 2 units , then the magnification will be 12/2 = 6.When the focal length of the main lens is constant , the focal length of the eyepiece is inversely proportional to the magnification.
Why do convex lenses have shorter focal lengths than thin convex lenses?
The convex lenses are converging lens so when the curvature of the lens increases the focal length will decrease which helps when looking up close. A thin convex lens is for seeing things from a distant.
