Talk:Magnifying glass

2007 post

For the following:

The highest magnifying power is obtained by putting the lens very close to the eye and moving the eye and the lens together to obtain the best focus. The object will then typically also be close to the lens. The magnifying power obtained in this condition is MP0=¼Φ+1, where Φ is the optical power in dioptres, and the factor of ¼ comes from the assumed distance to the near point. This value of the magnifying power is the one normally used to characterize magnifiers. It is typically denoted "m×", where m=MP0. This is sometimes called the total power of the magnifier (again, not to be confused with optical power).

Magnifiers are not always used as described above, however. It is much more comfortable to put the magnifier close to the object (one focal length away). The eye can then be a larger distance away, and a good image can be obtained very easily; the focus is not very sensitive to the eye's exact position. The magnifying power in this case is roughly MP=¼Φ.

A diagram of these two cases would really be helpful.

--Erland Lewin 20:40, 21 October 2007 (UTC)

I would really like to draw these diagrams. However, I'm having some trouble understanding exactly what's going on (presumably why there needs to be a diagram!). Can anyone clarify what needs to be done? Or point me to where I can read more? Thanks. --CheCheDaWaff (talk) 18:05, 13 April 2016 (UTC)

If you don't already know what needs to be drawn, you are not going to be successful at producing the required drawings.--Srleffler (talk) 00:17, 14 April 2016 (UTC)

Creation

It would be nice to know how magnifying glasses are made to have that concave shape. Is there a section in a "glassmaking section" or what? —Preceding unsigned comment added by 41.241.43.175 (talk) 14:26, 21 January 2008 (UTC)

I think the claim "magnifying power is the ratio of the image size on retina with and without lens" conflicts with the claim that "magnifying power depends on the distance from eye to lens".

if the power is defined as the ratio, the ratio is fixed as long as the object-lens distance is fixed, since the virtual image size is fixed.

yes, normally we do want to put our eyes closer to the lens, but that is only in order to have a larger view angle, because if you view through the lens from a distance, you would be able to view only a small portion of the virtual object----- just imagine viewing a real object through a small hole in a black wall. the area of the lens is the small hole. I think the author mixed the idea of the "actual size of the retina image" with the concept of "ratio" when defining the magnifying power

burning

many people use these to reflect the sun and burn things —Preceding unsigned comment added by 121.218.222.125 (talk) 07:15, 22 December 2008 (UTC)

Antakya

Welche Temperatur erreicht ein Brennglas durch die Sonnenstrahlen? 1000 Grad Celsius, 2000 Grad Celsius, 3000 Grad Celsius, 4000 Grad Celsius, 5000 Grad Celsius, 6000 Grad Celsius?

• http://de.wikipedia.org/wiki/Lupe#Verwendung_als_Brennglas —Preceding unsigned comment added by 193.122.47.146 (talk) 12:52, 23 December 2008 (UTC)

"Magnification" and "magnifying power"?

I think the author of the article Magnifying glass tries to differentiate between the two terms. According to the article Magnification, the evaluation of the magnifying power, i.e. the "ratio", assumes the image position to be exactly 25cm to the eye (near point). This is called the normal use of an optical instrument.

Actually, an optical instrument can have many possible magnification, which can be demonstrated by using the simple thin lens formula (1/u + 1/v = 1/f). Magnification M = |v/u| = f/(f-u) , where u (object distance) can be varied to achieve different magnifications.

The magnifying power is defined this way (having a fixed ratio) because sometimes we have to compare the "power" of different types of optical instruments, say a simple magnifying glass vs a microscope.

Antony css (talk) 13:08, 29 January 2009 (UTC)

History of Telescopes seems confused

The history of Telescopes has the same names and information as page 33 of Renaissance Vision from Spectacles to Telescopes By Vincent Ilardi, but the information becomes all mixed up, suddenly vases described by scientists are attributed to comedians who we know described disposable convex glass lenses. I'm going to be back to try to make sense of it, but I want anyone on the page to admit that the version stating that the comedian Aristophanes invented a magnifying tool in the same year that he wrote about a cheap lens at the pharmacy, for a joke in a play, that info is contradictory, and probably just wrong. Lotusduck (talk) 17:36, 3 January 2014 (UTC)

History

The examples from Aristophanes and Pliny only refer to burning lenses, not magnifying glasses. I suggest that these be removed from this article. Kortoso (talk) 22:03, 1 June 2015 (UTC)

The article doesn't claim that they were magnifying glasses, but they are precursors to the magnifying glass. The quote from Seneca given in the article makes it clear that the ancients were aware of the applicability of these devices to magnifying images. --Srleffler (talk) 05:35, 2 June 2015 (UTC)

Fresnel lens

The explanation of why does a fresnel lens works is wrong. It is not a stack of lens. It works based on light interfere. Guilloip (talk) 02:56, 20 March 2016 (UTC)

No, it doesn't.--Srleffler (talk) 04:26, 20 March 2016 (UTC)

Best image

User:Svjo replaced the image of a postage stamp being viewed through a lens with an image that he/she made, showing what appears to be a simulation of text being viewed through a magnifying glass. I do not feel that the new image is better than the one it replaced. Do any other editors have an opinion?--Srleffler (talk) 00:37, 10 September 2016 (UTC)

Citation needed for use as a symbol

citation needed for use as a symbol Asterisk482 (talk) 04:16, 1 April 2019 (UTC)

Done.--Srleffler (talk) 05:17, 1 April 2019 (UTC)

Magnifying glass

What is it?? 129.0.76.143 (talk) 19:19, 12 January 2022 (UTC)

Wiki Education assignment: Introduction to Information Studies

This article was the subject of a Wiki Education Foundation-supported course assignment, between 15 January 2024 and 9 March 2024. Further details are available on the course page. Student editor(s): SalasJoshua (article contribs).

— Assignment last updated by JDav39 (talk) 00:53, 30 January 2024 (UTC)

Image should be better

In this February 2020 edit a user replaced the "CG illustration with photo" - which I agree should be done. Unfortunately the replacement image is actually also CG, just more realistic. If anyone wants to take a similar, high quality photo, that would be very cool. GanzKnusper (talk) 14:52, 8 July 2024 (UTC)

I'm not a fan of the cat photo that was recently added. Too similar to the photo below of a person looking through a lens. Ideal would be a photo of a magnifying glass in front of a book or other object where it is clear that the view of the object is magnified. Ideally the object should be in focus and the frame of the magnifying glass not excessively blurry.--Srleffler (talk) 21:19, 20 July 2024 (UTC)