What is Focus: Definition and 202 Discussions

FOCUS is a fourth-generation programming language (4GL) computer programming language and development environment that is used to build database queries. Produced by Information Builders Inc., it was originally developed for data handling and analysis on the IBM mainframe. Subsequently versions for minicomputers and such as the VAX and other platforms were implemented. FOCUS was later extended to personal computers and (in 1997) to the World Wide Web: the WebFOCUS product.

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  1. S

    B Diving into ellipsoid swimming pool at one focus

    [ just a fun question :) ] Thinking of the focussing properties of ellipses - If a swimming pool was shaped liked a large half-ellipsoid...and someone dived in at a focus...would the splash then largely appear at the other focus ? In fact would a swimmer at the second focus then be projected up...
  2. C

    Trying to review linear algebra after graduating

    TL;DR Summary: linear algebra confusing & hard; how to study right? I plan to return to linear because that was one of the classes that you couldn't just try to shamble your way through somewhat. multivar calculus theorems still make some sense visually. Linear algebra exams were like trying...
  3. J

    What programming languages/pathways should I focus on?

    I am a Senior in High School looking to go to college for Computer Science. Since Freshmen year I have been learning Front End Development (HTML, CSS, and Javascript), albeit somewhat slowly and staggered due to school getting in the way and whatnot. In the past year, I have learned some more...
  4. N

    I Two mirrors to focus sunrays into a tiny spot -- possible?

    Hi guys, i am Nenad Komjenović from Bosnia and Herzegovina, I am just a regular guy, who likes geeky stuff and i don't know physics, so i wanted to ask you guys for an opinion. I was inspired by the "Markus Kayser - Solar Sinter Project" Youtube video, in which the guy used fresnel lens to...
  5. bigmike94

    Which topics are best to focus on in my spare time for engineering?

    Summary: Which are the best engineering topics to really focus on during my spare time to prepare for the real world. Im on a physics and engineering degree, but will hopefully be doing a masters in engineering, my engineering modules are all the standard broad ones that most engineering...
  6. L

    B Infrared Cameras -- Do they use a Lens to Focus?

    Can infrared cameras focus IR radiation as a visible light camera focuses visible light? I think IR doesn't pass through glass well? What are these germanium lens about? I don't think my Flir IR camera has a lens.
  7. OscarV

    Which Undergraduate Degree Path is Best for Fluid Dynamics and Plasma Physics?

    Hello, My university offers degrees in the following: Physics with mathematics, Physics with theoretical physics, and physics with computer science. I am interested in fluid dynamics and plasma physics and lean more to the theoretical side. I would like to build a versatile toolkit in order...
  8. LCSphysicist

    Relativity General relativity with focus on action?

    I am having a class of general relativity. It seems that the professor will follow an approach which consist of achieve the action, and variate it to get the equations of motion (indeed, that's how we already got the geodesic equation, the dynamics of a particle in electromagnetism, the equation...
  9. PhysicoRaj

    Stargazing Level of details in prime focus vs eyepiece images

    I hope this is the right place to ask this. I was clicking the Sun a few days ago with my beginner scope and a DSLR. The scope is a 60mm aperture f/12 refractor and the DSLR is a Canon SL3 (APS-C 6000x4000). First I used a 20mm eyepiece (35x) to view the sun, saw it in all its glory, the...
  10. D

    B Observing Orbital Mechanics from the 2nd Focus of Earth's Orbit

    If a hypothetical spacecraft could keep station at the 2nd focus of Earth's orbit, what useful observations could be made? Each minute sees a new solar triangle Earth Sun Craft (ESC). Swept area remains constant, as should length SC, and length CE + ES. With the Sun as our point source...
  11. Carolus_Rex

    Studying Focus on in-depth understanding of the Maths behind Physics

    As a Junior year physics undergrad, how much should i focus on understanding the maths behind the physics i use. One one hand i believe that understanding maths behind the physics i use is necessary but sometimes specially in calc i feel that i am going in too much. Simply speaking from your...
  12. P

    Why 0.3m From Lens Is Optimal Focus?

    Apparently, it must be placed at the focus (0.3m away from the lens). Why is this so?
  13. Vissarion

    Aerospace Engineering Subfields -- Which ones should I focus on?

    Summary:: Aerospace Engineering Subfield I am Sttudying Aerospacce Engineering and I must Follow a specific Subfield of Aerospace Engineering The main Course Structure of each Field is: Structures and Materials 1. Mechanical Behavior of Materials 2. Lightweight Aerostructures 3. Advanced...
  14. L

    Focus or parallelize the light from an LED

    Hello, everyone, I have a LED, 620nm, with a viewing angle of 20°. I would like to bring this light in a distance of about 20cm on a lens with as many photons as possible. My idea is to position a converging lens between the LED and the lens. To be exact, I would position the lens at the...
  15. P

    Programs What should my focus be during my PhD?

    Hello everyone! So I recently finalized attending UIUC for my PhD in Astronomy. Before beginning my undergraduate studies, after learning about what I needed to do in order to get into a successful PhD program, I made the following and laser focused on them: -Maintaining a 4.0 cumulative GPA...
  16. P

    Finding the height of a focus point via ray tracing @ Snell's Law

    So far all I can work out is that the angle of incidence of the outer two and inner two rays is zero degrees, however, I can't work out how to get started on the problem. I feel like I need to use vertical slowness rather than the normal snell's law since I'm working with a dZ rather than a dX...
  17. C

    Understanding Ultrasound Focus and Intensity in Tissue Exposure

    Is ultrasound focus just like light rays where the intensity is strongest in the focus? How much is the exposure when the tissue has only a partial ultrasound beam passing (like cross section, imagine 1/4 of beam sides) through it. For example. The focus of the ultrasound is deep in the kidney...
  18. Vividly

    Intro Physics Physics books that focus on Concepts mostly rather than equations

    Im looking for a book that gives descriptions and explanations of physics concepts instead of a equational representations. Or A book that focuses mostly on concepts with minimal equations. I have come across Richard F. Lectures that are red textbooks and I am looking for other alternatives...
  19. D

    Physics Is a physics career's main focus Discovery and not Invention?

    Is the main focus of the physics career discovery, leading invention for the engineers? I mean in the hypothetical situation of the building of a rocket, would the physicist spend their time discovering new ways of making combustion or discovering new materials for a spaceship, and the...
  20. E

    Can Math Model Real-World Camera Focusing Dynamics?

    This problem arose in modeling camera focusing movement, such as a control system might do. It assumes a simple (thin) lens, rays close to the optical axis, and monochromatic light. While most camera lenses are not simple, this is a first approximation. Camera lenses project an image of a...
  21. S

    MHB Find vertex, focus, and directrix of parabola: y^2+12y+16x+68=0

    Find the vertex, focus, and directrix of the following parabola: y^2+12y+16x+68=0 The form we have been using is (y-k)^2=4p(x-h) Any explanation would help too, I'm really stuck on this one. Thank you!
  22. S

    A What is the relationship between focal length and focus point in convex lenses?

    First of all, Let me present some of the things I found from research. (considering convex lens) Interpretation 1 => Focal length is the distance from the center of the lens to the point where all rays converge. Interpretation2 => Focal length is the distance from the point of convergence to...
  23. Dipra Irham

    Why Does a Prism Periscope Focus Light Instead of Scattering It?

    a prism is supposed to scatter light rays and separate it into rainbow,then why in a prism periscope the prism send light rays to a particular direction instead of scattering?
  24. S

    I Print something to be seen in focus by person w/o glasses?

    Is it possible to print something with an ordinary laser printer that is blurred in such a way that it can be seen clearly by someone who ordinarily requires a strong prescription to correct their eyesight but would appear a blurred mess to someone with normal eyesight?
  25. N

    Could you focus light from Sol's corona?

    For instance, if you put a big "magnifying glass" above the atmosphere in the shadow of a total solar eclipse thus blocking out light from the "surface of the sun", could you heat an object to a temperature hotter than the surface of the sun? Applying the Second Law, one can't raise the...
  26. Adgorn

    Polar equation of a hyperbola with one focus at the origin

    Homework Statement Hello everyone, I have an assignment (Spivak's Calculus) to show that the polar equation of a hyperbola with the right focus in the origin is ##r=\frac {±\Lambda} {1+εcos(\theta)}##, but the equation I reached was slightly yet somewhat disturbingly different, and I'm not sure...
  27. D

    I Explanation for the hyperbolic array of light rays.

    Hello, Recently, a solar power tower plant was founded next to where I work. Since it's the tallest object in the area, it's quite hard to miss it. But apart from that, every morning the reflected light is arranged in a hyperbolic- like way, as you can see in the picture. Does anyone have a...
  28. S

    Programs Broad Interest and Environmental Focus

    Hello! I am returning to school but have, unfortunately, not decided what my end goal is. I originally enrolled in mechanical engineering, and dropped out to pursue a marijuana pipe dream that was unfulfilling. Now, at 19 YO going on 20, I am re-enrolled in community college to fix my GPA and...
  29. Z

    The coefficient of kinetic friction for a Ford Focus

    Hi guys, Yesterday I sat down, and just for fun, decided to calculate the coefficient of kinetic friction for the all electric Ford Focus. I keep getting the wrong answer, and it is driving me crazy. Here are the facts. Battery: 23 kWh. Curb weight: 1,651 kg. Maximum travel distance before a...
  30. S

    Schools I want to focus on Fluid and/or soft body dynamics

    Hi, I finished my first Bachelor in Physics, than continued my studies by finishing second bachelor in mechanical engineering. I am a very enthusiastic pilot, maybe that's the reason why I'm pulled towards fluid dynamics and soft body dynamics. Well my dilemma is the following: I don't know...
  31. V

    Optical geometry of smartphone camera.

    I posted the following on a phone forum and got no replies, as expected. It's a bit out-of-the-way and technical. Thought this might be a better place since the question still interests me. I'm using my phone to take photos of assembly procedures on my electronics workbench. However, the focus...
  32. S

    Testing To focus on general GRE Writing?

    Hi all, Maybe most people would say that physics grad schools (PhD) programs don't care about your GRE writing score, but I have a sort of quick question: how much effort should I put into the Writing sections. I took my first GRE earlier this month, but messed up both of my writing sections...
  33. Philip ebuka

    Other I find myself in a science 'no focus' country.

    I'm from Nigeria, and currently in my second year studying physics Its so unfortunate that my country has no interests whatsoever in science, and its affecting the whole science education system. Nearly everyone wants to study medicine, or any engineering course, because those are the only...
  34. stevendaryl

    Lenses and Pinholes: What Does "In Focus" Mean? - Comments

    stevendaryl submitted a new PF Insights post Lenses and Pinholes: What Does "In Focus" Mean? Continue reading the Original PF Insights Post.
  35. N

    External focus in an optical system

    I feel a bit stuid for asking this. I have an optical system conisting of a laser source, a lens with some focal length F and aperture stop `(with some diamater D), followed by another lens (with another focal length) f and aperture stop d at some distance r from the first aperture stop D. What...
  36. Pakano

    Extreme focus of a radially polarized beam

    What happen if a radially polarized beam is extremely focused to a single spot? Is it disappeared because E-fields in opposite direction subtract each other?
  37. S

    Studying How to focus when science is not your end goal?

    Hello, I'm interested in political philosophy. However, I very strongly respect rationality and the scientific method, and want my impact on the world to be maximizing its application to society in order to optimize our civilization. In order to do this, I am completing a bioengineering...
  38. X

    Other Got starting job, need focus for next step

    Hello everyone! I graduated in June with a M.S in Biomedical Engineering and obtained a starting job that I started three weeks ago as a quality control analyst related to the testing of pharmaceuticals in a company called ICON Plc. While it sounded good at the time of applying for the job there...
  39. S

    How to focus and direct microwaves?

    I am interested in building a microwave powered toy helicopter purely for the fun of it. As we have discovered in our initial research, it isn't possible to direct the microwaves from a microwave oven magnetron too far. I know that those microwaves are of a similar wavelength (or is it?) What...
  40. M

    Keep losing focus when doing math

    I keep finding myself losing focus in the middle of doing even basic maths. I sometimes know exactly how something should be done, but make stupid mistakes doing it because I can't fully concentrate. I used to have an obsession with numbers (as a kid) and was great at mental maths. Now, I'm...
  41. O

    Engineering Power Quality with focus on harmonics

    Hi Anyone got any suggestions/recommendations for literature either available for free online or books that I have to buy? My background: Electrical engineering student, working on a project that is about analysis of power quality with focus on harmonics.
  42. mr.tea

    Courses What courses are necessary for a math student interested in CS?

    Hi, I am a math major student. I am interested in the theory of computer science and I would like to go to this direction in graduate school. So I need some advice about what courses of computer science I should do, and what courses of mathematics I can ignore. My program has a lot of freedom...
  43. avito009

    I Focus of Earth's elliptical orbit

    If the orbit of the Earth has only one focus which is the Sun then why can't it move in a circular path. Since a circle has only one focus and that is at the centre. Why is the sun the only focus when the path of Earth is an ellipse?
  44. parshyaa

    I Is it possible for an ellipse to have only one focus?

    i think there is only one focus of ellipse and we can draw a ellipse with a single focus. please correct my thinking.
  45. D

    Hello, question about engineering focus

    Hi all, I am starting civil engineering B.S this fall. I am very interested in mechanical as well but there are no nearby schools. Does anyone know if you can get your B.S.C.E and then get your M.E?
  46. S

    Ellipse from 2 arbitrary points, tangent at P1 and focus

    MENTOR Note: Moved this thread from a math forum hence no template Is it possible to find this? Really only need the semi major axis or even it's orientation. In the image below, elements in red are known.
  47. DigitalPanda213

    Studying A changing focus from Art to Engineering

    Alrighty, here we go. I'm currently a junior in high school (going into my senior year this fall), and my plan was always to become an artist as i thought it the way i could make a change in the world; however, I've begun to think pursuing engineering (particularly electrical) will enable me to...
  48. F

    Can You Focus on Two Distances at Once?

    Homework Statement You are standing approximately 2 m away from a mirror. The mirror has water spots on its surface. True or False: It is possible for you to see the water spots and your image both in focus at the same time. Homework Equations p=object distance q=image distance The Attempt...
  49. Q

    Studying What should I focus my efforts on?

    Hi, I'm a sophomore physics and computer science major. I go to a "well-regarded" university in the top 20 (I'll keep it anonymous unless you guys think details might help), yet I don't feel like the academic experience has been particularly stellar. I loved my freshman multivariable calculus...
  50. BlueQuark

    Finding the focus of a parabola given an equation

    Homework Statement Alright, so the equation of a parabola is y = 1/4p*x^2, P being either an x or y value, and the other x or y being zero. Let's say that x^2 = 16y. If you divide both sides by 16, you get y = x^2/16, which can be simplified to y = 1/16*x^2. This is in the format of a parabola...