Sunlight Definition and 105 Threads

I have recently learned that taking vitamin D supplements can cause a dip in magnesium, because Mg is used as a cofactor to process the vitamin. Does this apply to a sudden lifestyle change from very little exposure to lots of exposure to sunlight? (I am asking this as a purely theoretical...

I recently stumbled on a problem I can't solve. For background, there is a recent story from July 8 about 99% of people receiving sunlight at 11:15 am. Anyone can google it and it's explained fairly well at time and date. There is an illustration. Here...

If the Sunlight lets say would go off, exactly how long would astronomers on Earth still see sunlight reflected on the surface of Mercury, Venus, Mars, the asteroids, Jupiter Saturn, etc.? I mean Sun goes dark at 0:00 from the point of view of Earth-based observers. At that exact moment, if...

How did you find PF?: Google Hello, I am new here. I am wondering, how is it possible for nearly 70% of the spherical Earth to be illuminated by the sun every July 8th? How can a sphere be illuminated beyond 50% with a single light source. How do we explain this?

Hi Pfs, I know that Young made his double slits experiment with sunlight and i would like to know the best value of the fringe visibility on the screen. The visibility is equal to (Imax - Imin)/(Imax + Imin) thanks

Hello- I am starting a project to get direct sunlight onto the house by placing convex mirrors on the outside stone fence of the backyard since it is the only place of my property that is not shaded by other houses in the neighborhood. For that, I need to calculate the size of the mirrors...

What are the common and/or possible chemicals that could release from clothes or bedclothes when it is exposed to sunlight? Since there are many different textures and additives so I am concerned about the common chemicals that could release I roughly know that sunlight will break a lot of...

With the total visible light flux being equal does reflected sunlight (by the sky, environment or shading/light redirecting surfaces) have a smaller total energy per luminous flux and therefore resulting heat gain than direct sunlight? Possibly caused by a larger luminous efficacy, i.e. more...

A photon is different from an electron. At least by the fact that it is neutral. But, flying into the silicon lattice, it knocks out an electron and takes its place. That is, it becomes an electron. How does such a magical transformation happen? I may be wrong, but I think that a photon becomes...

Is reflected sunlight on any surface otherwise than mirror or mirror-like surface safe for human eye? I can imagine mirror surface could reflect a lot of sunlight directly, making little difference from staring at the sun directly How about reflected sunlight on white but obaque surface? Could...

This is an older idea of mine which I just remembered when reading the thread about using a light-bulb to make a laser. The concept is this: 1: Focus light from the sun into a point using a magnifying glass, which we know can burn things. 2: at the point of focus, place another lens which will...

Hello. I am a filmmaker writing a screenplay and I am in need of technical support to validate a method being used in the film. I am going to post this in the Earth Science forum but I'll copy it here, in case anyone reading this might know. Thank you all! "I am wondering if shadows cast...

Is the reason you can make out the shape of the sun and the moon is because the gaps between the leaves cause the light to be photons instead of waves?

Today when I was standing beside a container in sunlight I observed that the shadow of my hand merged at a certain distance with of the container even though their was enough distance between my hand and container for light to pass is there a reason?

With talk of the Earth's magnetic field slowly moving, (enough to cause navigational issues I've heard) does it effect how the sun's ray hit us? For example, the Northern Lights are solar partials interacts with the magnetic field (I think). If the poles moves, would it affect the effectiveness...

“Sunlight due to refraction is greater in higher latitudes than at the equator because of shallower angles of incidence to horizon. It takes longer for Sun to go down half a degree at sunset at shallower angles.” When I draw a diagram of sun rays incident towards the earth, the angle appears to...

In school we are taught that sunlight contains all different frequencies of light. Also that each frequency has it's own unique wavelength and energy (per photon). So my question is that if there are infinitely many different wavelengths of light (much like infinitely many numbers in an...

hello! I find a lot of information about the energy of sunlight per square meter in the UK region. (https://photonenergy.co.uk/new-build-solar-pv/solar-map-of-the-uk) However, these kWh/m2 must be in the form of light energy or perhaps electricity (after adjusting with an efficiency...

Hello, Let me first describe the situation I am thinking of: suppose we consider an object in the form of a square with some thickness (e.g. a mirror). Suppose further, that the gravitational force pulling the object towards the sun and the radiation pressure due to the sunlight are in balance...

If I am walking on a sunny day, looking mostly straight ahead, and the Sun is close to straight ahead but elevated 30 to 45 degrees so I'm not looking directly at it, is there a risk of vision damage?

How long is a beam of light or sunlight?

Hi. In physics articles, they say that sun light is white, and contain all colors. But they show say that the Sun's atmosphere absorb light at certain wavelengths, causing the intensity of the light at this wavelength to drop and appear dark. And the absorption spectrum looks like this...

Hello Is it possible to direct sunlight into the optical fiber by magnifying glass and a prism like the image below? if yes , what shape of prism should i use to do this? Thank you

On the Moon, could you melt dirt into bricks and paths by focussing sunlight? If you had a large metal parabolic reflector and just pointed it at the ground, would it melt the dirt? Could you make a path that way? In the vacuum there would be less escape of heat to cool it. If you piled dust...

I read in a book about a man who saw the sun reflected off a distant object on a mountain some 73 miles away in clear visibility. He saw this on many occasions and always wondered what it could be. He states that he asked two of his friends who were going that way if they would check it out...

Hello, Would a set of inexpensive xenon lamps purchased at the hardware store simulate sunlight pretty well in terms of spectrum (visible and IR) and intensity? Solar simulators are expensive devices but I wonder if I can get by with an array of less costly xenon lamps. thanks

Homework Statement Estimate the rms electric field in the sunlight that hits Uranus, knowing that the Earth receives about 1350 W/m2 and that Uranus is 19.2 times farther away from the Sun (on average) than is the Earth. Homework Equations I=cεoErms2 E=V/d The Attempt at a Solution Eearth=V/d...

i have this idea to produce fresh water for farming and all the other uses of fresh water, from seawater, on sunlight, using mostly/only off-the-shelf parts.. i am currently not able to pursue this idea myself due to financial constraints, so i thought i'd float the idea here looking for some...

Yesterday morning the lighting from the sunlight made everything brighter until 11:50am Pacific Daylight time. I am in the San Francisco Bay Area in Northern California. Can you explain why sunlight on 13 July 2016 appears to be 'brighter' than this morning?

This 400-700nm slice is the Photosynthetically Active Radiation (PAR) required of plants and, for many applications, there is much unwanted UV and IR heat outside of it. Is there any known translucent material or film that will pass a high % of that 400-700nm wavelength from sunlight while also...

With the growing threat of global warming, couldn't we launch a series of rockets into space filled with water and have them discharge the water to create clouds in space between the sun and earth? The water vapor cloud would absorb and deflect some of the heat. It wouldn't have to be very...

We all know the famous theory that an asteroid hits the Earth and kill the dinosaurs by starting a chain reaction where the dust is all over the atmosphere preventing sunlight to reach plants causing them eventually to die thus causing herbivorous to die thus causing carnivorous to die. But when...

This is my school's assembly area : The place is generally used for the assembly and various other things. But the problem is that it receives a lot of sunlight and it is difficult to use it during the later part of the day. So, I would like something like a roof, which doesn't entirely...

So I had this idea and I want to run it by some people and see if it's 1) possible 2) worthy of pursuing further 3) a good idea. I don't have a degree in engineering or physics, I'm currently studying chemistry and am taking physics 2 (E&M) right now, so excuse me if I don't use the correct...

Hello! First of all I want to say that I am not a physicist, but an artist currently doing my master thesis. I have been trying to build a solar powered slide projector. It works very simple – I reflect sunlight through a slide and enlarge it with a lens. My problem was that I wanted more...

Hi! I have a question regarding the radiation coming from the sun. It might seem stupid to some people but I would really like to know how this works. When you see images of the sun's rays reaching the Earth for example on this image from wikipedia (see attached image). The rays are almost...

Homework Statement Which has the most intense sunlight hitting it?Question 2 options: A point on the Equator at sunset The North Pole at Noon on the Summer Solstace Montreal at Noon on the Spring Equinox The South Pole on the (Northern hemisphere) Summer SolstaceHomework Equations none The...

Homework Statement Question: Lake Mead is formed by the Hoover Dam, and while it actually changes in area and volume, consider it has an average area of 100,000 acres. Assume that 250 W/m^2 of sunlight falls on Lake Mead, how much electricity could be produced if this lake area was covered by...

Can anyone explain how we acquire vitamin D or which chemical reaction takes place ?

Can anyone speak on the spectrum of sunlight reaching the upper atmosphere and the surface ? Specifically I interested in finding out if there are any IR wavelengths disproportionally represented when compared to the original source. Please limit responses to constructive ones.

Hi all, I'm implementing a computer vision system with a near-infrared laser and a NIR bandpass filter. It shines a laser on things and looks for a reflection. I'm getting a bunch of interference from sunlight and was thinking of using a polarizing filter to cut some of the sunlight out...

It seems like it should be easy to use two lenses to 1: focus light into a small point then 2: use a stronger lens past the focal point to keep the beams fairly parallel. Experimentally, I have not been able to achieve these results. I have an LED flashlight which can project a fairly tight...

My son is working on his science fair project. I had told him that LED bulbs produce voltage in sunlight and he's been exploring that and is trying to see if he can charge a cell phone using LED bulbs under a light source. Using dozens of small LEDs, he is producing about 5v under a light...

First, let me just say that, while I tend to be knowledgeable on a wide variety of topics, I am absolutely atrocious with details such as names, times, and specific values. A friend of mine has decided that I'm imagining an effect that I have experienced on countless occasions and which I...

Sunlight contains UV radiation. UV lamps are used to destroy the reproductive organs in pathogens. Therefore, in desperate times could one remain in the sun to keep a wound clean?

Hi, I was wondering what the diffraction pattern would be like if the suns light is diffracted through a pin hole or double slit diffraction grating compared to that of a laser beam? thanks.

Simple question will UV glue that is supposed to be dried under a UV light dry or harden if taken and placed in direct sunlight? John

Last month I bought one of those pens which you can rub off your writings with a kind of rubber at the end of the pen. I was so happy because I don't need to use correction pens anymore, so I did all of my maths exercises with that pen. One Friday, my books was very heavy so i left some inside...

A blackbody radiator emits radiation across the entire radiation spectrum. The "temperature" of the blackbody radiator (measured in kelvin) can be directly calculated from the peak wavelength of its radiation using http://en.wikipedia.org/wiki/Wien's_displacement_law"]Wien's[/PLAIN]...

Hello, For my Mechanical Engineering project, I'm working on a wind tower. One of the specifications we have to respect is a 50 years resistance to sunlight. We've chosen inox steel as the primary material (after calculating the various constraints due to the wind the the rotor up on the...