What is Sunlight: Definition and 106 Discussions

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. When direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. When blocked by clouds or reflected off other objects, sunlight is diffused. Sources indicate an "Average over the entire earth" of "164 watts per square meter over a 24-hour day".The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a requisite for vitamin D3 synthesis and a mutagen.
Sunlight takes about 8.3 minutes to reach Earth from the surface of the Sun. A photon starting at the center of the Sun and changing direction every time it encounters a charged particle would take between 10,000 and 170,000 years to get to the surface.Sunlight is a key factor in photosynthesis, the process used by plants and other autotrophic organisms to convert light energy, normally from the Sun, into chemical energy that can be used to synthesize carbohydrates and to fuel the organisms' activities.

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  1. E

    Steel wind tower resistance to sunlight

    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...
  2. L

    Help Derivatives - maximizing sunlight through a window

    Help Derivatives ASAP -- maximizing sunlight through a window 3. The amount of daylight a particular location on Earth receives on a given day of the year can be modeled by a sinusoidal function. The amount of daylight that Windsor, Ontario will experience in 2007 can be modeled by the function...
  3. D

    Evidencing interference pattern using Young's slits and sunlight - help required

    I am an artist with some knowledge of physics and I am trying to build a pinhole camera to expose photographic film using sunlight that passes through a filter, pinholes and Young's slits. I would like to photograph an interference pattern using the sun as the subject. My prototype camera...
  4. K

    What is the hottest you can make a focused beam of sunlight?

    Some have said it was 6000 degrees K. I'm not so sure. I know for sure that you can increase solar intensity arbitrarily by using lenses and mirrors. What I don't get is why this doesn't increase temperature beyond a certain point. Is it somehow related to the photoelectric effect? I guess...
  5. P

    Calculating Light Intensity from Sunlight for Solar Food Dehydrator

    Hi there, im doing school project regarding Solar Food Dehydrator. Can tell me what is the formula to calculate the light intensity from the sunlight?
  6. A

    Solar Spectrum: The source of sunlight

    What is the source of sunlight? The answer is Solar spectrum. Can anyone explain how the crimson color is created? actually what happen when the sunlight is created? Need help from the expert.
  7. B

    Create Sunlight: Artificial Possibility?

    would it be possible to artificially create 'sunlight' by the use of several lamps? for instance a bulb/cfc rich in blue light, another rich in red light, one rich in green light, by the use of UVb/UVa lights and infrared lights, and then, by the means of deflecting the specific lights (after...
  8. dillmon

    Amplifying Sunlight Through Fiber Optic Cables w/ Resonance?

    Here is my question: Can light of multiple wavelengths (for example sunlight) that is transferred through a fiber optic cable be amplified equally with resonance? If this is not possible, are there other methods besides resonance to achieve this effect. If optical resonance is used, how do the...
  9. J

    Temperature of a body exposed to sunlight

    hello, If I have a black painted aluminium exposed to sunlight (being it and the atmosfere at 27ºC), and I have the total solar radiation it is exposed to (lets say 1 ° KW-hr/m²), how can I know the evolution of its temperature? (if there is any free simulator on the internet I would be glad...
  10. A

    Which is better for concentrating sunlight ?

    which is better for concentrating sunlight ?? I m doing a project on solar illumination . I wanted to know which configuration of parabolic reflector/ collector is better in terms of efficiency - central axis (cassegrain) or off axis ??
  11. K

    Photoelectric effect, and sunlight.

    Hello, I apologize if this question makes no sense, or is stupid, but I would just like to clarify something. Is the light that comes from the sun a high enough intensity to "knock" any electrons out of the atoms in a metal? I know it is a high enough frequency, and I think the intensity is...
  12. baywax

    Why does heat reflect sunlight? (ie: mirages)

    The title of this thread is all I have to ask about this. You've seen mirages, if they are caused by light reflecting off heat I am wondering why this takes place. Thank you.
  13. H

    How Much Has Atmospheric Pollution Reduced Sunlight Reaching the Earth?

    I don't no if this is the right place to ask this question or not I want to know that over the past number of years, how much less sunlight is reaching the ground because of the fine particles that we are placing into the atmosphere? Over the past 5, 10 15 or even 50 years, how much sunlight is...
  14. DaveC426913

    *Where* does sunlight scattering occur?

    I observed a strange phenomenon the other day which led me to ask this question. I was in Bahamas on a cruise, where it is very bright. This might have enhanced an otherwise more subtle effect. (OK, get the drinking jokes out of your system now... :tongue:) I was outside, right next to...
  15. V

    Sunlight equivalent light bulb

    If the 'average' intensity of direct sunlight on a warm summer day could be re-produced in a full spectrum light bulb, how many watts would that bulb be? I'm trying to find a bulb I can use to calibrate a photo sensor to sunlight intensity but my shop is on the base floor where there are no...
  16. M

    Coherence Sunlight Refraction homework

    Homework Statement On the wet road / asphalt / there is a oily stain,with refraction coeff 1.4 .Sunlight lights up the grease perpendicular .What colour will be a stain with thickness of d = 250 nm ? The water's refraction coeff is 1.33 Homework Equations Since we are asked what colour...
  17. G

    Calc Power Output of 1 Square Meter Solar Panel on Earth

    Let's say we have a 1 square meter solar panel on Earth's surface. The sun is shining brightly and it's the middle of the summer. Let's say this solar panel is 100% efficient. What is the total power output by this solar panel? How would you go about calculating it? Would it matter if it was...
  18. Simfish

    Medical What does sunlight do that incandescent light can't do?

    What does "sunlight" do that incandescent light can't do? Both of them emit light at roughly blackbody distributions, and their light distributions both seem centered in a way such that they both produce white light. Light therapy produces a lot of excess light at the higher frequencies. But...
  19. C

    Is it same if i cover my car or let it open on direct sunlight?

    would the heat generated by covering my car under the sun would still fade its paint? since maybe its more hotter inside the plastic cover since there's no air circulation would this still make my car paint fade more?
  20. S

    Harnessing Sunlight Indoors for Sustainable Gardening

    I am aware that fiber optic cable can channel sunlight indoors. Is there any sort of end point which could throw the light out in all directions? Maybe a substance in the center of a room that if you redirect sunlight onto it via a mirror, the light would scatter and fill the room? And...
  21. R

    Exploring the Mass of Sunlight: A Thought Experiment

    Thought experiment: Our sun burns hydrogen at a prodigious rate, billions of kilograms per second. Let m = the mass of the sun at t=0. Inside the imaginary sphere expanding exactly with the velocity of light emanating from the sun, the total mass cannot change. After sixty seconds...
  22. I

    Sunlight falls on a concave mirror, where is the image formed?

    Homework Statement Sunlight falls on a concave mirror and forms an image 3.0 cm from the mirror. If an object 24 mm high is placed 12.0 cm from the mirror, where will its image be formed? a. Use a ray diagram b. Use the lens/ mirror equation c. How high is the image? Homework Equations...
  23. D

    What would be the force on a beam of particles from focused sunlight?

    What would be the force imparted on a beam of particles from focused sunlight? For the sake of argument all particles are going at the same speed. For the sake of argument you utilize the 'full ' spectrum of the sun (or at least, most of it). Thanks for your time and effort DWM91
  24. S

    Max temperature attained by focusing sunlight?

    Can one focus sunlight so much that the temperature attained at the focus is higher than the temperature on the surface of the sun? Consider this question in the framework of geometrical optics (no diffraction, no solar panels or electricity). This seemingly innocent problem is actually quite...
  25. J

    Solar Voltaic Cells - converting sunlight to electricity over a given area

    Solar Voltaic Cells -- converting sunlight to electricity over a given area Homework Statement 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...
  26. I

    Calculate Pressure Increase of an Aerosol in Sunlight

    Homework Statement An Aerosol has a of pressure 250kpa at 17 C.The aerosol is left in the sun and its temp.rises to 27 C.Calculate new pressure in the can if its a 35% increase in the amount of vapour present. Homework Equations P/T= constant The Attempt at a Solution well tbh i...
  27. P

    Comparing Light Spectra from Incandescent Bulbs, Fluorescent Tubes & Sunlight

    Homework Statement What are some differences between the spectrum observed for light from the incandescent bulb, the fluorescent tube, and the spectrum observed from sunlight? The Attempt at a Solution I think that sunlight produces an absorption spectrum, whereas both incandescent bulb...
  28. G

    Fading Ink on Book Covers: Sunlight Cause?

    I have a book with a green cover. I left it on a window sill in direct sunlight for about a week and now the colour on the exposed side has clearly faded. Why does this happen? Is it something to do with the Ultra Violet properties of sunlight destroying the pignments in the ink?
  29. F

    How much energy can a black metal surface absorb from direct sunlight?

    I'm trying to figure out a simple way to estimate how much energy (in the form of heating water) can be collected by a black metal surface of a given area exposed to direct sunlight during the day. Any thoughts?
  30. R

    Can a parabolic surface help reduce heat from sunlight?

    If I should reflect our suns' rays off of a parabolic surface, and placed a one way mirror at a distance away, short of the focus point. Let's say a 10cm disk is placed at that point parallel to the parabolic rim. The light would tend to reflect back at the parabolic surface but would the...
  31. S

    Can sunlight be turned into other things besides energy.

    Trees turn sunlight into "tree food". They turn sunlight (which is basically nothing) into something. Maybe if we manipulated the process of photosynthesis, we could make trees turn the sunlight into other materials (and maybe in the far future we could have trees making metals for us). Thoughts?
  32. mheslep

    Sunlight reduction in large volcanic events

    Last night I watched the fun, if not reliable, history channel piece on volcanic eruptions large enough to significantly reduce sunlight. I'm curious. What's a rough order of magnitude of sunlight reduction expected from the various size of events? Some quick googling gives me: Small...
  33. J

    Do photosynthetic plants require natural sunlight

    I'm certain this is a silly question but: Do photosynthetic plants require natural sunlight to undergo photosynthesis, or will artificial light from flourescent lights suffice? Thanks!
  34. A

    Calculating Mass Increase of Earth Annually From Sunlight

    Homework Statement By how much does the mass of the Earth increase each year as a result of sunlight reaching it? Radiation from the sun reaches the EArth at a rate of 1400W/m^2 of area perpendicular to the energy flow. Assume 100% absorption. Homework Equations I'm sorry but I haven't...
  35. U

    Detailed rainfall, sunlight, and temperature data?

    Where do I find such data, for the European area? I need region specific information, for as small as possible regions.
  36. T

    What is the energy density of sunlight on Earth and near the surface of the sun?

    [SOLVED] Energy Density of Sunlight Homework Statement Use the solar constant (1350 W/m^2) to calculate the energy density of sunlight at a)Earth and b) near the surface of the sun. Homework Equations Stefan-Boltzman = (2pi^5)/(15(h^3)(c^2)) h=6.63x10^-34 j.s L(solar...
  37. S

    Start-up says it can make hydrogen with sunlight and water

    http://www.news.com/8301-11128_3-9852737-54.html The Maynard, Mass.-based company, which Wednesday announced that it has raised $4.7 million, has come up with a low-cost, durable titania electrode that can split water molecules into hydrogen and oxygen. Sunlight hits the electrode, and...
  38. D

    Concentrating sunlight to creat different extream temperatures

    I am wondering of a way to concentrate sunlight to an extent to create high temperatures that vary depending on how many mirrors, lenses...etc i use and so on...it is an idea i have for a physics project any suggestions on how i might go about this would be muchly appreciated.
  39. S

    Sunlight bulbs-is this real?

    Hey guys, I have been hearing about those bulbs that give sunlight benefits. However, there are so many of them that it is hard to know which one is a good one. Surprisingly, most of them are fluorescent so I don't suppose that's good for our health. The halogen ones are rare. And there are...
  40. C

    Estimating the ratio of flux of sunlight to moonlight (at full moon)

    I'm trying to estimate the ratio of the flux of sunlight to moonlight (at full moon). What I'm interested in is if I'm doing the physics right. I know what the solar flux is at the surface of the Earth (actually, just outside the atmosphere): roughly 1400 Watts/m^2. I can actually calculate that...
  41. C

    Maximizing Solar Energy Efficiency: A Thermodynamics Question"

    Thermodynamics question: How much work can be obtained from sunlight? It seems like a solar panel within the sun would not continuously generate electricity (else it could purely convert heat to work) but instead would emit as much black-body radiation as it absorbs. Back here the light is...
  42. R

    What main wavelengths are within sunlight (p.s. not a hw problem)

    I ordered these giant fesnel lenses online. They are about 2.6 by 3.3 feet, and can supposedly melt asphalt. I was just wondering what is the main wavelength that causes the energy: visible light, ultra-violet, infrared, some other that I don't know about, or all of them?
  43. C

    Does sunlight push the Earth ever so slightly?

    Considering that the Sun radiates EM photons at many different wavelengths onto the Earth and that these photons carry a momentum which they impart into the Earth upon contact, wouldn't the aggregate of all these 'pushing' photons create a noticeable effect on the the Earth's graviational orbit...
  44. Doc Brown

    Question about reflecting sunlight off a mirror

    First off, I apologise for this basic (and rather random) question. I am not educated in this area, in fact I have no education in physics whatsoever, but an idea for an invention came to me over the weekend and whether it is feasible or not depends on the answer to this question. I have enjoyed...
  45. I

    Sunlight a catalyst for vitamin C oxidation?

    hi can someone please help me with this question "does sunlight affect oxidation of vitamin C" I have seen this as a common science fair topic and I have also done an experiment myself and have found that it does speed up vitamin C oxidation, But I don't know why! can someone please help me...
  46. T

    Sunlight Intensity: Measuring for Window Facing South

    A research center measures sunlight intensity every hour every day. The measuring device stands on flat ground and therefore measures light accordingly. The output is W/m^2. The problem is that I need to utilize this value for a vertical window on a wall facing south. How can I best do this?
  47. T

    A pyranometer, a device that measures sunlight intensity

    I am to use a pyranometer, a device that measures sunlight intensity. I am confused about the output unit it produces. It says on it's side 4.55 \cdot V/\left( {W \cdot m^{ - 2} } \right) but I'm not sure how to interpret this unit. All help will be appreciated...
  48. 1

    Sunlight Intensity: Calculate Total Average Power Output of Sun

    I need help with this problem... Suppose that the intensity of the sunlight that reaches Earth's upper atmosphere is approximately 1200 W/m2. Earth is about 1.5 times 108 km from the Sun. What is the total average power output of the Sun, assuming it to be an isotropic source?
  49. T

    How to Measure Sunlight in Watts for a Room

    I need to measure the amount of sunlight that enters a room over a given period. I assume I'll need to get my hands on some device which can measure this, but in the meantime, is there a way to approximate how much light/energy enters the room at a given time? The best would be to get a Watt...
  50. F

    Estimating & Calculating Leaf Temperature in Sunlight

    A leaf of area 40 cm2 and mass 4.5 x 10-4 kg directly faces the sun on a clear day. The leaf has an emissivity of 0.85 and the specific heat of 0.8 kcal/kg.K. a) Estimate the rate of rise of the leaf’s temperature. (ans: 2.3 oC/s) b) Calculate the temperature of leaf would reach if it lost...
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