0
What do you mean by an equivalent lens and equivalent focal length?
Wiki User
∙ 7y ago
It means that if you combine two or more lenses (one after the other), the effect (for many purposes) would be similar to a single lens that has such-and-such properties.
Wiki User
∙ 7y ago
Add your answer:
Earn +20 pts
Which lens concave or convex forms the image wider?
Only a convex lens forms any kind of real image and the size of the image is dependent upon the focal length (hence the curvature and and substance) of the lens. A concave lens forms a virtual or imaginary image in front of the lens. It is one that cannot be projected onto a surface. Perhaps what you mean has to do with convergence and divergence. A convex lens causes light rays to converge (come together at a point), while a concave lens causes rays to diverge.
How can you find focal length of a converging lens?
To find the approximate value of the focal length of a convex lens, let us do an experiment. Place a convex some distance away from a light source. At the opposite side of the lens, place a white paper. Now adjust the position of the lens till a sharp point of light on the white paper is obtained. Measure the distance between the lens and the white paper. This gives the value of the focal leng
What does focal mean?
singing loudly
Why is the focal length of a plane mirror infinity?
In a plane mirror, the radius of curvature is infinitly long, so the focus will be at infinity. Another way to say it is that a plane mirror has no curvature, and as curvature becomes increasingly small, focal length becomes increasingly long. At a curvature of zero, focal length becomes infinite. Focal length(f) is given by f=R/2 where R is radius of curvature.. Once again, it's infinity! See answer to your question on radius of curvature. Plug infinity (radius of curvature) into your mirror equation to get the focal length, which will also be infinite. A flat mirror does not focus incoming parallel beams. That's because if you say its at infinity it means it does exist in a finite distance, that is instead of saying it does exist its taken at infinite distance for only theoretical importance and not for practical observance. Focal length is half of radius of curvature of the mirror. So bigger the circle gets the more its radius will be. So in the same way as the curvature of the sphere gets less and less its focal length increases, so when it becomes totally flat the focal length will become infinite so it means it has no existence but it has only theoretical importance. It same as taking the formation of image of an object at principal focus to be at infinite distance rather than saying it does not form ( that is both mean the same). hope my answer is satisfactory
What are the different steps in a ray diagram?
Given the position of the lense:Draw a base line (a straight line) with the size of object (shown by an upright arrow) and any other information given (focal length, postion of lense etc.). If given, skip to next stepExtend the lense (can be omitted, skip if given)Draw the first ray through the middle the lenseDraw a second ray to the lense parallel to the base line, then draw a line, cutting the focal length of lense (at the opposite side of object)Draw a third ray down the focal length before the lense, then a parallel line after the lenseThe image would be at the intersection point of 3 lines (2 lines would also mean the formation of an image)If they seem to spread further out, the image would be formed at the same side of object.
What is the Local length of the lens?
i think you mean FOCAL LENGTH.
What do the numbers followed by mm mean on a jewlers loupe?
The focal length of the lens in the loupe
What does 'par focal' mean?
A parfocal lens is a lens that stays in focus when magnification/focal length is changed. There is inevitably some amount of focus error, but small enough to be considered insignificant.
What does mm mean for a digital camera?
MM refers to the focal length of the lens. In the old, old days of Paul Rudolph's original Tessar lens, "focal length" meant the distance between the middle of the lens and the "focal point" - the point at which all the rays of light coming out of the lens converge on one spot. That lens was first introduced in 1902, and since then we've learned that different focal lengths of lenses have different angles of view...so now, if a lens has an angle of view equal to that of a 50mm lens, we call the lens a "50mm" regardless of the actual length of the lens.
What does mean the mm e.g. 18 -200 mm camera or 55-200 mm?
That number is the focal length of the camera's lens ... which focuses light from the scene to form an image on the 'film' or CCD inside the camera. The longer the focal length of the lens, the larger (nearer) the objects appear to be in the picture. (One radian of angle as seen by the lens ===> One focal length on the film.) On the cameras described in the question, the focal length is given as a range ... "from 18 to 200 mm", and "from 55 to 200 mm". Each of these is a "zoom" lens, whose focal length can be changed over the range, enabling the user to cause objects in the picture to appear somewhat nearer or farther away.
What does 75 -300 mm mean in relation to camera lenses?
This is a Zoom lens with a focal length of between 75 and 300 mm.
What does parfocalization mean?
A parfocal lens is actually a lens that stays in focus when there is change in the magnification, or focal, length. The amount of focus error is so small in fact, its considered insignificant.
What does the mm mean on a camera lens?
The "mm" marking represents the focal length of the lens as measured from the optical center of the lens to the film plane when the lens is focused at infinity. If the lens is a zoom, focal length is expressed as a range such as 28 - 80mm, which means it can be infinitely varied from one length to the other. Most zoom lenses accomplish this in part by varying the position of the optical center. The focal length or zoom range is typically indicated on the lens barrel and/or the area surrounding the front lens element. Lenses that accept accessory filters are almost never marked with a filter diameter or series size on the lens, though screw-in filters have the diameter indicated in millimeters on the filter rim. Since many lenses are stored with a filter in place, this might easily be mistaken for a part of the lens itself, particularly with screw-in filters, which normally sit flush with the front diameter of the lens barrel.
What does 18-200mm f mean?
That describes a telephoto lens with the lower and upper focal lengths.
How do glasses help short sighted people?
Short sighted people are not helped by lenses or anything else. Except the consequences of their short sightedness. I think you mean near sighted people. The eye is a lens and focal point system. The focal length of the eye can be manipulated by flexing muscles in the eye socket to change the distance between the lens and the back of the eyeball. A near sighted, or even a far sighted, person has an eyeball that is too long or too short for the lens, and therefore the image produced by the eye's lens is focused either in front of or behind the back of the eye. A lens, either in a pair of glasses or a contact lens, can assist the eye by effectively pre-focusing the image that enters the lens of the eye to a sharpness that can be accommodated by the focal length of the malformed eyeball, focusing the image sharply on the back of the eyeball. - wjs1632 -
Which lens concave or convex forms the image wider?
Only a convex lens forms any kind of real image and the size of the image is dependent upon the focal length (hence the curvature and and substance) of the lens. A concave lens forms a virtual or imaginary image in front of the lens. It is one that cannot be projected onto a surface. Perhaps what you mean has to do with convergence and divergence. A convex lens causes light rays to converge (come together at a point), while a concave lens causes rays to diverge.
What does it mean when a camera is marked f equals 35 mm?
F = 35mm means the focal length of the lens is 35 millimeters. The focal length is the distance from the place where light enters the lens through to where the light rays converge in a point. For most people, the number (35mm) simply indicates the size of the lens and what type of images you can expect to get with it. For example, in a 35mm SLR camera, the "normal lens" is 50mm. "Normal" simply means when you look through the viewfinder* the lens makes the perspective you see look natural. Nothing appears closer or farther away; nothing appears distorted. Lenses with a focal length shorter than 50mm (35 mm, 20mm, etc.) are called "wide angle" lenses, because they allow the film (or sensor**) to record a wider angle of view than the normal lens. Lenses with a focal length longer than 50mm are called telephoto lenses (110 mm, 200 mm, etc), because they allow the film/sensor to record more of a close-up view. This is an oversimplified explanation, but should give you a general idea of what f = 35 indicates. * Assuming you're not looking through a rangefinder. ** Digital sensors that are less than full frame use a multiplier that varies based on sensor size (e.g., 1.5, 1.6), so a 35 mm focal length will give different results when used on a digital camera. This is just a note -- we'll save the full explanation for another question.
