A dioptre (British spelling) or diopter (American spelling) is a unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, 1 dioptre = 1 m−1. It is normally used to express the optical power of a lens or curved mirror, which is a physical quantity equal to the reciprocal of the focal length, expressed in metres. For example, a 3-dioptre lens brings parallel rays of light to focus at 1⁄3 metre. A flat window has an optical power of zero dioptres, as it does not cause light to converge or diverge. Dioptres are also sometimes used for other reciprocals of distance, particularly radii of curvature and the vergence of optical beams. The main benefit of using optical power rather than focal length is that the thin lens formula has the object distance, image distance, and focal length all as reciprocals. Additionally, when relatively thin lenses are placed close together their powers approximately add. Thus, a thin 2.0-dioptre lens placed close to a thin 0.5-dioptre lens yields almost the same focal length as a single 2.5-dioptre lens. Though the dioptre is based on the SI-metric system, it has not been included in the standard, so that there is no international name or symbol for this unit of measurement—within the international system of units, this unit for optical power would need to be specified explicitly as the inverse metre (m−1). However most languages have borrowed the original name and some national standardization bodies like DIN specify a unit name (dioptrie, dioptria, etc.) and unit symbol dpt. In vision care the symbol D is frequently used. The idea of numbering lenses based on the reciprocal of their focal length in metres was first suggested by Albrecht Nagel in 1866. The term dioptre was proposed by French ophthalmologist Ferdinand Monoyer in 1872, based on earlier use of the term dioptrice by Johannes Kepler. (Wikipedia).
From playlist Trigonometry TikToks
How Is the ADHD Brain Different?
If you’re online, you may notice that conversations around ADHD are everywhere. You may even be starting to wonder, as you flick from one app to the next, that you yourself may have ADHD. So in Part 1 of this series about ADHD, Julian explores what this disorder is, what’s happening in the
From playlist Seeker+
Metacognition and speaking | Introduction | Part 1
In this video, I provide an overview of metacognition and discuss its role in speaking.
From playlist Metacognition
UCI Physics 3C: Basic Physics III (Fall 2013) Lec 14. Basic Physics III View the complete course: http://ocw.uci.edu/courses/physics_3c_basic_physics_iii.html Instructor: Michael Smy, Ph.D. License: Creative Commons CC-BY-SA Terms of Use: http://ocw.uci.edu/info More courses at http://ocw
From playlist Physics 3C: Basic Physics III
I want to help you achieve the grades you (and I) know you are capable of; these grades are the stepping stone to your future. Even if you don't want to study science or maths further, the grades you get now will open doors in the future. Get exam ready for GCSE Maths https://primrosekitt
From playlist Maths (The Physics Bits) for Science Students
This video shows how trigonometry is both interesting and useful. Its history, practical uses, place in mathematics and wide use are all covered. If you are wondering why you might want to learn trigonometry, start here!
From playlist Trigonometry
The Creation of Historical Effects - D. G. Burnett - 4/26/2019
On April 26-27 2019, the Division of Humanities & Social Sciences at Caltech hosted a conference in honor of Jed Z. Buchwald, “Looking Back as We Move Forward: The Past, Present, and Future of the History of Science.” This event was sponsored by the Division of the Humanities & Social Sci
From playlist Looking Back as We Move Forward - A Conference in Honor of Jed Z. Buchwald - 4/26-27/2019
Episode 5: Sines And Cosines Part II - Project MATHEMATICS!
Episode 5. Sines and Cosines, Part II: (Trigonometry) This video focuses on trigonometry, with special emphasis on the law of conies and the law of sines, together with applications to The Great Survey of India. The history of surveying instruments is outlined, from Hero’s dioptra to moder
From playlist Courses and Series
Trigonometry 4 The Area of a Triangle
Various ways of using trigonometry to determine the area of a triangle.
From playlist Trigonometry
Episode 8: The Tunnel of Samos - Project MATHEMATICS!
Episode 8. The Tunnel of Samos: This video describes a remarkable engineering work of ancient times: excavating a one-kilometer tunnel straight through the heart of a mountain, using separate crews that dug from the two ends and met in the middle. How did they determine the direction for e
From playlist Courses and Series
Using the Pythagorean identity to verify an identity
👉 Learn how to verify Pythagoras trigonometric identities. A Pythagoras trigonometric identity is a trigonometric identity of the form sin^2 (x) + cos^2 (x) or any of its derivations. To verify trigonometric expression means to verify that the term(s) on the left-hand side of the equality
From playlist Verify Trigonometric Identities
Trigonometry 5 The Cosine Relationship
A geometrical explanation of the law of cosines.
From playlist Trigonometry
Trigonometry - Vocabulary of trigonometric functions
In this video will cover some of the basic vocabulary that you'll hear when working with trigonometric functions. Specifically we'll cover what is trigonometry, angles, and defining the trigonometric functions as ratios of sides. You'll hear these terms again as we dig deeper into the st
From playlist Trigonometry
Lec 8 | MIT 2.71 Optics, Spring 2009
Lecture 8: Telescopes; aberrations: chromatic, spherical, and coma Instructor: George Barbastathis, Colin Sheppard, Se Baek Oh View the complete course: http://ocw.mit.edu/2-71S09 License: Creative Commons BY-NC-SA More information at http://ocw.mit.edu/terms More courses at htt
From playlist MIT 2.71 Optics, Spring 2009
Holographic Approach to QCD matter (HQCD - Lecture 4) by Johanna Erdmenger
PROGRAM THE MYRIAD COLORFUL WAYS OF UNDERSTANDING EXTREME QCD MATTER ORGANIZERS: Ayan Mukhopadhyay, Sayantan Sharma and Ravindran V DATE: 01 April 2019 to 17 April 2019 VENUE: Ramanujan Lecture Hall, ICTS Bangalore Strongly interacting phases of QCD matter at extreme temperature and
From playlist The Myriad Colorful Ways of Understanding Extreme QCD Matter 2019
E.O. Wilson: On The Shoulders of Giants
Every generation benefits from the insights and discoveries of the generations who came before. “If I have seen a little further it is by standing on the shoulders of giants,” wrote Isaac Newton. In a special series, the World Science Festival invites audiences to stand on the shoulders of
From playlist Explore the World Science Festival
New definition of a parabola with focus and directrix
Learn all about parabolas in conic sections. We will discover the basic definitions such as the vertex, focus, directrix, and axis of symmetry. We will also take a look a basic processes such as graphing, writing the equation and identifying a parabolas parts when given an equation in sta
From playlist Learn all about Parabolas #Conics