Focal Definition and 292 Threads

Hello, I am new to this forum and know very little about it. But perhaps somebody can help me. I have an Epson 2040 projector. The beam it projects fits into the screen at a distance of about 4.5 meters. But logistically I need to put it at 8 meters from the screen, so the projected images are...

My attempt: m=-v/u=-f/(-f-u) -1/0.5= -f/-f-0.10 -> -f-0.10=0.5f -> f=0.20 m

I would like to realize an image of the cantilever. The dimensions are (450x50) microns. I would like to use a self-constructed telephoto lens. This consists of two lenses. The image magnification can be 4 to 8. The magnification of the image is nothing more than the ratio between the two focal...

I noticed on the commute home today a car with a LCD rear view mirror and I wondered whether, if I were driving it, I'd be able to focus on it the same as I focus on my car's glass review view mirror? I need glasses to read, and that includes a computer, so figured a LCD screen that close, even...

Hello, I need a bit of help. My age and fading competence are showing (no complaints, just facing up to it). I have an optical SETI observatory in Panama with a 20" Newtonian and a piggybacked 14" Cassy. I wish to mask a portion of stellar Airy disks with an E-W wire on a small photometer...

In this problem, it doesn't tell you where is the focal length. So how do you know if it is in front or behind the object?

I was just checking out this experiment for finding focal length of a lens that I did few years back. the method used was called as the u-v method(https://www.concepts-of-physics.com/pdf/uv-method.pdf), and here in this method, object distance u and image distance v is measured from the sharp...

Here I was going to use ##\int \vec F \cdot d\vec l = \frac{1}{2}mu^2## What I got that is ##l=\frac{mu^2}{2eE}##. Here the question is what is ##l## (I took ##x## while doing the work but here I used ##l## instead of ##x##)? I was assuming that it's ##x## since I am calculating work in the...

Hello Everybody, I'm David from Spain, and happy to be here. We have a LED that needs a FL50mm collimator which is focused to infinite, because we want parallel rays. So the lens is at a distance 50mm (approx) from the led. However, 50mm is too much distance for our design, so the question is...

I am covering parabolic antennas with a school student in elementary physics, and I was looking for the specs of the (offset) antenna on her family's roof in order to calculate things like focal distance. She sent me a photo (she is on another continent), I found the brand specs, which lists it...

I have an extremely fast (f/1.05) night vision optic that I scavenged from a old night vision unit which is faster than current production lenses (f/1.23). However due to the design of newer night vision tubes, the lens will not focus to infinity on the night vision tube. This is because the old...

I wanted to calculate the focal length and focal point of the collimator. The collimator diameter is 3mm, and I wanted to focus on the 100-micrometre active area of the detector.

Hello. I need formulas for the focal length of a lens when I have refractive indices of two centers and two radii of curvature of spherical surfaces or one radius of curvature of spherical surfaces. I search the internet but can't find it.

##\frac{1}{f}=\frac{1}{u}+\frac{1}{v}## ##f = \frac{u.v}{u+v}## Let: u + v = w → w = 250 mm ± 8 mm Percentage uncertainy of v = (3/50) . 100% = 6% Percentage uncertainty of u = (5/200) . 100%=2.5% Percentage uncertainty of w = (8/250) . 100% = 3.2% Percentage uncertainty of f = 6 % + 2.5 %...

The above image (source) is pretty much the only thing we're told about how the MAPK pathway is activated. However, in passing, FAK was mentioned. We were told that focal adhesion integrins activate FAK which then activates the MAPK pathway. Seen in the image (source) below However the two...

The picture below shows a so-called chromatic doublet, which is designed to minimize chromatic aberration, ie the wavelength dependence of the refractive index of the glass. The first lens has a flat first surface and a concave second surface with radius of curvature R and index of refraction n1...

1/f = 1/dₒ + 1/dᵢ = 1/1.0 + 1/0.33 = 4.03 m (focal length) Power: 1/4.03 m or 0.248 (0.25) *around to the2 decimal points? or leave it as a fraction? ((Did I do this correctly? I am not sure if this is correct and is it okay to be in meters not centimeters?)) Please let me know!

Suppose one light up with a laser on a grid with grid constant g. The grating is followed by a focusing lens with a focal length of f. In the focus (or immediately in front of it) the maxima have a distance d. How large was the distance of the maxima immediately after the grating? scheme: Laser...

A physics question from Principles of Physics by Mazur in the chapter on Optics is asking me to "repeat Problem 92 for a diverging mirror", and one of the questions in Problem 92 (which is about a converging mirror) is to find the image distance of an object halfway between the focal point and...

Homework Statement: Propagation of Error for Focal Length Homework Equations: f = (s'*s) / (s' + s) In my lab, we had to calculate the focal length of a lens based on object distances (s) and image distances (s') that we measured. The object distances were measured with an uncertainty of...

Summary: Hi, I'm doing an assessment for Physics on Optics topics, but I can't really explain how the CV affect the RV CV : Focal length of convex lens RV : Temperature of water after 20 minutes under the sun How I should explain for the temperature difference? 🤔 Please help, Thanks.

Hello, The human eye has an average diameter of ##2.5 cm## and an optical power between ##60D## and ##64D##. An object can be brought as close as the near point which is about ##25 cm##. If ##d_{o}=0.25m## (object distance) and ##d_{i}= 0.025m## (distance to the retina), the optical power...

I tried -M=pq = f/(f-p) = f/f - f/p = 1-(f/p) => M+1= -f/p => -Mp-p=f But since it’s the y intercept, p will equal zero and so the focal length will be 0?

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...

Homework Statement A hyperopic eye has a near point of 1.10 m. Calculate the focal length of the spectacle lens required to correct the hyperopia (assume that the near point of the normal eye is 25.0 cm.) Homework Equations 1/f=1/p+1/q The Attempt at a Solution I just used .25 m as p and...

A bit of unsual scenario, I need to divide a video projection beam horizontally into two. Since the splitted beams in my diagram are treated as a separate beam they have to have their focus plane changed. Is that possible to do and how would one do it? http://image.ibb.co/jAu9x7/9241421.jpg If...

In order for a conventional telescopic riflescope to function, it must invert the image two times. As a result, the light-rays traveling through the tube must meet at two focal points. With my limited knowledge of optics, i assume that parallell light going in through the objective will meet...

The question: -------------------- The length of a microscope pipe is $L=160\,\rm mm$, the transverse magnification of its objective $M_o = 40\times$ and the diameter $d_o = 5\,\rm mm$. As for the ocular/eyepiece, its magnification is $M_e = 10\times$. 1. Find out the focal length of the...

Homework Statement An object is in front of a convex mirror. We then obtain an erect image whose height is equal to 25% of the height of the object. What is the distance between the object and the mirror if we know that the focal distance is equal to 0.2m? Homework Equations M = Yi/Yo = q/p...

So we have the focal lengths: f1, f2, ..., f7 = 25mm And the distance between the lenses: d1-2, d2-3, ..., d6-7 = 50mm I have figured out that if the system would be afocal if it had an even number of these lenses. This is because the focal length of two adjacent lenses is the same as the...

Homework Statement The medium-power objective lens in a laboratory microscope has a focal length fobjective = 3.75 mm. What is the focal length of an eyepiece lens that will provide an overall magnification of -125? Assume student's near-point distance is N=25cm. Homework Equations...

I have a Cassini PM-160 spherical mirror used in telescopes as the primary mirror. The mirror is concave with a radius of curvature of 2600mm and focal length of 1300mm. I have a very basic question. If an on object is located beyond the focal length of a concave mirror then the virtual image...

Homework Statement The distance between an object and its upright image is 28.0 cm. If the magnification is 0.550, what is the focal length of the lens that is being used to form the image? Homework Equations 1/f = 1/so + 1/si M= -si/so The Attempt at a Solution See included image...

Hello, suppose we are given a biconvex lens with focal length of 4 cm. Further, an arrow of height 1 cm is placed in front of the lens in a distance of 8 cm (i.e. twice the focal length). Lastly, a mirror is placed on the other side of the lens at a distance of 4 cm and such that it performs an...

Prove that tangents to the focal cord of parabola are perpendicular using the reflection property of parabola ( A ray of light striking parallel to the focal plane goes through the focus, and a ray of light going through the focus goes parallel) I don't know whether this is solvable with just...

Homework Statement 1) A double convex thin lens has a radius of 25 cm for the first surface and a radius of 40 cm for the second surface. If the glass has a refractive index of 1.55 the focal length is a) 28 cm, b) 9.93 cm, c) 121 cm, or d) 63 cm. 2) An object is placed 16 cm in front of a...

Hello, I would like to reduce the beam size of a laser by a factor of 10, with the purpose of replacing a long (750 mm) lens with a more compact design. Ideally I'd make a Galilean lens pair where the ratio of the focal lengths are 10:1 to produce a small collimated beam. However, I think I...

Hey, Not sure if this is the correct sub-forum to post this question. I'm still kinda new here, so sorry if I got it wrong :smile: I have a laser module with a fixed focal point of 16 mm and I'm trying to collimate that light into a beam. The point of focused light is at most a quarter...

So I'm working on a project where we're deciding a new lens to use for our laser diode. I need to determine the appropriate focal length based on the equation: 1/ƒ = 1/μ + 1/σ where ƒ is our focal length, μ is the distance from the lens to image and σ is distance from lens to object. For the...

Does the orientation of a plan convex lens affect it's focal lenght? If I put il like in the first example in the photo and makeep the calculation using the lens maker equation I get f positive What happens if I turn the curved face on the right? Using the lens maker equation now the radius...

I have fabricated a few biconvex lens (12mm diameter) for an experiment and am trying to find their focal lengths. My though is to set up three parallel lasers and find where the beams converge. However, even with the smallest laser diodes I could find, three beams surpass the diameter of the...

Homework Statement You are required to set up a light source, an object grid, a converging lens and a screen so that a quantitative investigation of object and image distances can be performed. Tabulate corresponding object and image distances (p and p' respectively). Also tabulate values of...

Homework Statement Calculate the focal length of a planoconvex lens that produces a real image 2.5 times as big as the object if the object is 2.5 cm from the lens? Homework Equations The only one I can think of is 1/f = 1/v + 1/u The Attempt at a Solution [/B] My 'attempt' is 1/f = 1/62.5...

Recently I have had a lot of eye strain from excessive computer use. The problem is because your eye lenses re stuck in a fixed position. I wanted to know if it would be possible to make a screen that is 1m away look like it is 4m away for example. Would it be possible by making the screen out...

Is it possible to magnify an object if the magnifier is sitting directly on top of the object (a focal length of zero)? How can this be accomplished if it is not possible with a traditional magnifier?

Homework Statement An object is at a very large distance from a concave mirror of focal length 40cm. Find the distance from the image to the mirror. Is the image real or virtual? Homework Equations 1/u + 1/v = 1/f The Attempt at a Solution [/B] 1/u + 1/v = 1/40 The image has to be real...

Homework Statement [/B] I was doing http://stao.ca/VLresources/sci-tie-data/lessons/1400_1499/DivergingLensExperimentDeta.pdf experiment. Let's look at this image: Suppose we get the imaginary object at dv by convergence lens. And this object is like a real object for the concave lens. Then...

Did not know how to word this properly. Looking for an equation to show the behaviour of how EM can be "lensed" as a function of wavelength/frequency. ie RF waves can not be lensed/focussed to a spot. what equation determines the minimum spot size a lens can focus EM radiation as a function...

Hello, I am pretty new to physics but have a large amount of experience with Calculus and other sciences like chemistry. The theory I have come up with is that if I combine 6-8 5w laser beams together in a convex lens that can be moved forward or backward to change the focal point distance, I...

Homework Statement A telescope has a focal ratio of f/7.5. You wish to use it with a spectrometer that requires a f/10 beam as its input. Compute the focal length of a 50mm diameter lens that, when inserted into the beam 150mm in front of the unmodified focal plane, produces the required beam...