Radiation Definition and 1000 Threads

The atomic nuclei consist out electrons, protons and neutrons (with only exception of hydrogen, that does have a neutron). Thus, it would be straightforward, that there existed a corresponding radiation for each nucleus component, when a nucleus decays. There is an electron radiation (beta...

Hi! My question is: I understand that at noon-day it’s hotter because of the angle with which sun rays enter our atmosphere. But at the same time, I was wondering that the band of radiation responsible for heating things is infrared, and that at noon basically all bands of lower frequency than...

Hi, I'm new here. I have a doubt regarding solar radiation, I heard in an astronomy class on the use of this solar radiation for the stabilization of satellites in orbit due to mechanical problems with their stabilizers. Electromagnetic waves emitted through solar radiation stabilize such a...

I am exercising on Stellar Physics topics and in particular the questions below: 1) First of all on the rotation profile for the radiative zone: I know that unlike the convective zone, where the rotation varies mainly in latitude (faster at the equator than at the poles), the radiative zone...

Is it just me or lately there is a big fuss about this? I keep running into news of a recent study that has found smartphones may induce cancer on rats and so on... Did they really find something relevant or is it just the same old story?

Hi, I have been solving one problem recently. I need to calculate, how many times faster is the aging under my UV lamp compared to the real sunlight exposure. I am pretty sure it will depend on the distance of the sample from the UV radiation source, it´s intense and exposure time. I would also...

The following are 3 equations of Planck's law or Planck's distribution function. Are they all correct? How do they derive from each other? Equation One: From page 512 of http://metronu.ulb.ac.be/npauly/art_2014_2015/shockley_1961.pdf We denote by Qs the number of quanta of frequency greater...

Homework Statement A light source radiates a sinusoidal electromagnetic wave uniformly in all directions. This wave exerts an average pressure p on a perfectly reflecting surface a distance R away from it. What average pressure (in terms of p) would this wave exert on a perfectly absorbing...

On another forum someone has been reporting on their efforts to characterise the background radiation in their lab prior to running some experiments. They don't have much data but what they have appears to have a daily cycle. They weren't looking for one and they haven't done enough work to...

Is the cosmic backround radiation incident on a black hole sufficient to make up for the energy lost through Hawking radiation? And what if we include the average energy flux from discrete objects like galaxies, as seen in intergalactic space?

In my heat transfer course, I always had to do analysis of long-wavelength radiation between surfaces first, and find the heat radiated from one of the surface. Then, solar radiation is added to the problem, and suddenly it was said that solar radiation=heat radiated from this surface! Does...

Homework Statement Q- a positron emerges normally from a 4-mm thick slab of plastic (density= 1.14g/cm^3) with an energy of 1.62 MeV. What is the energy of the particle when it entered the slab? Homework Equations Range when 0< T <= 2.5 MeV: R= .412+T^[1.27-.0954*ln(T)] where T is kinetic...

Suppose a point charge is slowly oscillating simple harmonically. Does it emit an electromagnet wave and if not why not ? How does its field change with time. Does anyone know of a good animation ? Thanks.

We're all pretty familiar with the harmful effects of UV radiation on biological organisms, including us. My question is whether there is any necessary or beneficial effect of UV radiation. That is, if our atmosphere suddenly started blocking out 100% of UV while passing all other radiation as...

Homework Statement A spherical body is enclosed in a spherical chamber which acts like a perfectly black body. The reflectance of the body is 0.4 and transmittance is negligible, the temperature of the body and surrounding temperature is constant at T Kelvin. The total power that comes out of...

Homework Statement What would be the increment in heat energy radiated when the temperature of a hot body is raised by 5%? Homework Equations P=σεAT^4 The Attempt at a Solution dP/P=4dT/T dT=5 when T is 100 initially. Let's assume P was also 100 initially for convenience, therefore dP should...

And if it does what is the mechanism and can it be used in astronomical spectroscopy?

as homework, I have to do the following exercise: Bremstrahlung emission : We are interested in ionized plasma of density ##n##, at temperature ##T## with ions of charge number ##Z##. 1. Explain the physical origin of bremstrahlung radiation 2. Represent the expected spectra (shape and...

Is melted bismuth safe to wear pretty much 24/7 around your neck ? I don't want to get a super low radiation hyper bug cancer fungus to appear after 30 yrs... (It touches your skin permanently unless you're running ofc) On top of that, can I smelt bare bismuth (99%) in my kitchen or should I...

Homework Statement Show that the radiation field is transverse, ##\vec{\nabla}\cdot\vec{A}=0## and obeys the wave equation ##\nabla^2\vec{A}-\frac{1}{c^2}\partial_t^2\vec{A}=0##. You should start from the expansion of the quantum Electromagnetic field. Homework Equations ##H=\frac{1}{2}\int...

I was thinking about how much propulsion you could get out of a solar sail, so I just did a rough calculation: A solar sail 100m*100m in size (10'000m²), with 20grams of weight per m², an additional 100kg for probe and other stuff, so 300kg probe weight. Using the solar constant of 1400W/m²...

I want to use small molecular - preferably CNT - "antennas" to produce THz signals to monitor activity in biological systems. After some googling, I've been reading things like "absorption spectra", "energy bands", "spectroscopy", as well as a bunch of antenna-science related jargon... I need...

Let me start out by saying that I have no idea what I'm talking about. I graduated from Indiana University with a Bachelor's in Spanish, and I work as a Loan Review Specialist at a bank, which has NOTHING to do with my degree, and still yet nothing to do with this topic. But lately, I've become...

Title says it all. Also, if the frequency of electromagnetic radiation is limited, why? My guess is the wavelength is limited to the Planck length, and when I plug those numbers into the calculator, I get 1.855 * 10^43 Hz. The maximum (Edit: observed) frequency of a gamma ray is 3 * 10^20 Hz...

It's my understanding that deforming a piezoelectric crystal causes electric charges to build up on the outer faces of the material. What I would like to know is if these charges behave like the free charges in a metal. More specifically, does deforming a piezoelectric crystal effect how em...

Hello everyone, Suppose a situation where you have a broad plane-parallele beem of electrons which is perpendiculary incident upon a thin foil which scatters the e- for an angle X. I did calculus and the ratio of flux density below the foil respect with the foil remove is 1.06. But, What are...

In Serway and Jewett's 'Physics for Scientists and Engineers', the authors state that "People all over the world have skin that is dark in the infrared, with emissivity about 0.900.' Similarly, in Louis A Bloomfield's 'How Things Work: Physics of Everyday Life', he states that 'Your skin is...

Homework Statement A perfectly reflecting solid hemisphere of radius R is placed in the path of a parallel beam of light of large aperture, if the beam carries an intensity I, what is the force exerted by the beam on the hemisphere? Homework Equations radiation pressure=I(1+ro)(cos^2(x))/c I...

I've read that nuclear waste is stored in Olympic-sized swimming pools, but what is it about water that so effectively stops radiation? And apparently, this shielding effect of water is so powerful that one could literally stand right next to the pool (and according to some things I've read...

In the field of medical physics, specifically in monte carlo simulation of radiation beams produced by electron accelerators, people call ‘phase space’ to a file that contains the data of a large number of particles when they traverse a reference surface in the machine (usually a plane), i.e...

Hi everyone, I have this question attached from the ABHP exam in part B you are asked to list and justify 4 major elements for accelerator radiation protection program for this specific facility, I have written some answers which are : 1) ALARA which includes : time distance shielding source...

I have seen many articles lately regarding planned manned missions to the moon and Mars but the question of radiation protection constantly comes up. Engineers keep proposing various shelter designs that use local materials (regolith) as a concrete base to absorb harmful radiation so that the...

Hello everybody, I have a question about thermal radiation: Imagine a body at a certain temperature T, in an environment with nothing around it. Theoretically, this body emits radiation according to its temperature (the maximum radiation is described by the Wien relation); If it emits, it must...

Consider two solid objects in the vacuum (of different materials, if you will) at different temperatures approaching each other until they make "perfect contact" through flat surfaces (no gaps or defects, so that thermal contact conductance effects are absent, even though interfacial thermal...

Am I correct that the direct proportionality between the energy and frequency of an EM wave can be obtained from classical electromagnetism? Of course there's the Planck–Einstein relation ##E = h \nu## for a photon, but that entails QM. I'm wondering about the relation ##E \propto \nu## for an...

Hello! I am reading Griffiths derivation for the electric dipole radiation (actually my question would fit for the magnetic dipole radiation too). He considers 2 charged balls connected by a wire with charge going back and forth between them. Now, when he calculates the vector potential he uses...

Homework Statement Homework EquationsThe Attempt at a Solution No . The number of photons should decrease . As the rate of heat transfer decreases with time , the net electromagnetic radiation from the hot body to the surroundings decrease . Heat radiations are composed of photons ...

I noticed HF radio waves travel farther and easier when the sun is out rather then during the night. Why?

I recently started learning about quarks and leptons and was wondering what happens to the fermions (specifically the quarks and leptons) during a beta decay. How is the electron/positron created and what causes the up quarks and down quarks to change flavours? If this is a bad question please...

Homework Statement Given: Cn_dot = true event rate = 10 interactions/s p(t')dt' = differential probability of an event Homework Equations p(t')dt' = Cn_dot * exp(-Cn_dot * t') dt' The Attempt at a Solution [/B] I want to sample the time interval using python. But I'm not sure how to go...

Hi everyone, I have an absorption spectrum that I obtained from a sample after radiation and I need to use the background sample as a reference, how can I do that using excel? what I did is subtract the radiated from the background spectrum then plot it, is that right? Thanks.

Can we use Gold Leaf Electroscope to check whether a radioactive material gives off Alpha particles?

Homework Statement 2. Consider a metal sphere of radius R and heat capacity C, initially at a temperature To which is much hotter than the background temperature. a) Derive an analytical result for the temperature of such a sphere as a function of time. Clearly state any simplifying...

What is the radiation and non-radiation terms in the equation B for a moving charged particle. How can I express the result in a tensor form? Thanks!

The following from Wiki re Hawking Radiation:“... vacuum fluctuations cause a particle–antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole while the other escapes. In order to preserve total energy, the particle that fell into the...

So I am planning on launching a Satellite to promote the Dogecoin cryptocurrency. One of the main points is printing/painting (Or whatever) the logo on the side of a metal panel. How can I make it so it doesn't melt off or turn white from radiation so quickly?

Homework Statement An impenetrable flat horizontal plate is radiated with 3000 W/m^2, where 500 W/m^2 is reflected. The surface temperature of the plate is 200 °C and it emits 500 W/m^2. Air with temperature 25 °C flows over the plate, and the heat transfer coefficient due to this is 20...

Homework Statement For a black body all absorbed radiation is emitted. Kirchoff´s law states that at the same temperature T1 the emissivity and absorptivity of a surface are equal, which holds for nonblack bodies as well. So, what really differs a black body and a non-black body in this case?

Hello Everyone, Sunlight is composed of UV, visible and infrared (IR) over a wavelength range from ~290nm to ~2500nm. When we are exposed to sunlight and feel hot, is it because of the absorption of energy at the visible wavelengths and FIR, i.e . infrared wavelength much larger than 2500nm? I...

Reading a thread in relativity I would like to know more precisely about radiation from charge. 1 I put a charge on the table of my house. Gravity and table reaction force work on the charge. They cancel so net force does not work on the charge, thus no-force no-velocity cause no radiation...