Focus Definition and 206 Threads

For example, Andrew Wiles worked on Fermat's Last Theorem for several years straight, or take Don Knuth, who has been writing The Art of Computer Programming (TAOCP) for an incredible 60 years. And here I am, constantly drifting from one subject to another, unable to stick with one thing for...

[ 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...

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...

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...

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...

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...

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.

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...

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...

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...

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...

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...

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

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...

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...

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...

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...

does someone know where can i find an introduction paper (i prefer in ps format) on the subject (but wich it would be more mathematical than physical)?p.s.and i have a few questions on the subject:1. how much is it different from euclidean geometry?2. can you recommend on someone who just...

I Drink a lot of coffeeHow does caffene work?What are the detramental aspects?Are there benefeits?Disclaimer: The opinions expressed above are not necessarily those supported by PhysicsForums.com

Could large mirrors be used to focus light from the sun into a high power laser?admin@physicsforums.com

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...

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...

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...

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...

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!

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...

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?

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?

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...

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...

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...

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...

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...

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...

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...

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...

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...

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

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...

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?

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...

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...

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...

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...

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.

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...

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?

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

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?

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.