1. J

    Apparent unruh radiation paradox

    What happens if you accelerate hard enough to produce a stable unruh particle with mass, ie an electron and then catch it and stop accelerating? Unruh radiation is only supposed to exist from the frame of reference of accelerating observers. From my understanding, unruh and Hawking radiation can...
  2. W

    Unruh radiation

    Does Unruh radiation imply that in an accelerating frame virtual particles become real or detectable?
  3. B

    Radiation and Convection problem

    I am trying to figure out what happens when a parcel of air rises in the atmosphere, and obtains potential energy due to its increased elevation loses kinetic energy proportional to the potential energy gained. Then while at TOA cools in accordance with radiation laws, then drops in the...
  4. M

    Deriving an expression for Radiation Pressure from Black body function

    https://photos.app.goo.gl/LWzgtJsCXs4zCCbc7 Hello, I am reading a book about Stellar Structure and Evolution and it takes an expression for the Black body function in terms of frequency and substitutes it into a 'Pressure Integral' to derive an expression for Radiation Pressure. It just...
  5. A

    Sunlight Radiation on lake of ice (how long time take ice to melt) Exam soon Help!:)

    Hi Everyone, I am new here and I hope I can get help here. Sunlight with intensity (600 w/m^2) Occurs an ice-covered lake. 70 % of the intensity absorbed of ice, which is 1.4 cm thick. How long time take to melt the ice? I know those formulas (not including in questions): P = I 4...
  6. O

    Temperature Increase due the radiation absorption

    Hello Everyone, I am trying to understand how to calculate the temperature increase due to the absorption of radiant energy by an object that can be approximated by a blackbody (emissivity and absorptivity close to 1). As radiant energy is being absorbed, the body temperature increases until...
  7. M


    BELOW I showing Ytube ( It was my inspiration to this post ) Dr. Quantum~Quantum Weirdness! https://youtu.be/3_BzTMeV4HI Important fragment ( please make pause 4:08 ) http://1.bp.blogspot.com/-OoDdkHJ9r8A/VQKwtR4BZdI/AAAAAAAACSU/WspWkyJcBho/s1600/c.jpg MY OWN...
  8. M


    Exist normal temperature Exist normal air's preasure Below I showing NORMAL EM RADIATION LEVEL and perpendicular to RADIATION SURFACE SIZE and AERODNAMICA SHAPE (aditional problems) my parameters are very important for each mechanical experiment ( special for high...
  9. W

    Which transfers more heat as a whole in the universe?

    Which transfers more heat as a whole in the universe? Conduction vs radiation The most obvious guess is radiation due to stars. Conduction seems to be considered negligible in stars but I've only read that in the context of energy transport to the surface and not necessarily just back and...
  10. H

    EM radiation

    Since the atoms of a magnet are exchange coupled,why it does not give off EM radiation? Does ferromagnetic and paranagnetic atoms give off radiation?
  11. E

    Cosmic rays: electromagnetic radiation or particles?

    Hi: In a physics textbook from 1968, a picture representing the electromagnetic spectrum, is divided into several regions: power transmission, AM radio, ..., X rays, gamma rays, cosmic rays, and the figure says: "The electromagnetic spectrum: ....... The scale ends in the vicinity of the...
  12. M

    Interaction of matter and radiation

    To whom is able to answer this: I think that when radiant energy get in contact with matter three basic phenomena take place: 1.- Transmission 2.- Reflection 3.-Absorption and emission I think this three basic phenomena enclose all phenomena that can occur after the interaction I wait for...
  13. kelsiu

    Radiation emission and absorption

    Any object can emit and absorb radiation and the power of emission can be represented by the Stefan-Boltzmann law: P=AεσT^4 In many texts the net power radiated is the difference between the power emitted and the power absorbed: Pnet=Aεσ(T^4-Ts^4) where Ts is the temperature of...
  14. R

    radiation blackbody

    before the invention of the electric freezer people used the techniquer of freezing water at night to form ice by alllowing the water to raidate its energy to night sky since the night sky acts asa black b0dy , the ambient temp is 6 degrress and the temp of the sky of -23 , if a mass of 4.5...
  15. G

    Blackbody radiation

    A blackbody is radiating at a temperature of 2.50 x 10^3 K. What fraction of the energy is emitted in the interval between 1.00 and 1.05 eV? I'm not sure how to approach this question.
  16. Y

    Please explain the Taylor expansion in Radiation

    For retarded scalar potential of arbigtrary source around origin: Where r point to the field point where V is measured. And r' points to the source point. For r' << r : This next step is where I don't understand how the book do the Taylor expansion. I am going to type the exact word...
  17. B

    Nuclear Physics: Dose Rate

    Q. A tiny radioactive source is embedded in flesh a few millimeters under the skin. The source is a 6.0 MeV alpha particle emitter of 3.7*10^-2 Bq (1pCi) activity. What is the dose rate and the equivalent dose rate? The rage of 6 MeV alphas in water is 3.9*10^-5 m. So I've tried solving this...
  18. D

    Energy And Electromagnetic Radiation

    3. How does each of the following relate to the amount of energy carried by electromagnetic radiation? a. Wavelength b. Frequency c. Velocity This is one of those questions in my physics assessment that the whole class is kind of wondering what to do. So far what I've found is...
  19. E

    Radiation from sun?

    I honestly have no clue how to do this... Can someone get me started in the right direction? I'm not even really sure which equations to use >.< A leaf of area 41 cm2 and mass 4.4 10-4 kg directly faces the Sun on a clear day. The leaf has an emissivity of 0.87 and a specific heat of 0.8...
  20. F

    Radiation and convection help

    hey im getting the answer 319 but the supposed answer is 219.12 please help me out Consider a person standing in a room. The room air temperature is maintained at 22OC at all times. The inner surface of the walls, floors and the ceiling of the room are observed to be at an average temperature...