Threshold Definition and 120 Threads

Does anyone have any information regarding if a photon will at some point obtain mass at huge energy amounts? Let's say perhaps the photon gains so much energy that it's wavelength reaches Planck's length, is it possible that it would gain mass? Is there any information regarding this inquiry...

Homework Statement (a) Show that E2 - p2c2 is a Lorentz invariant, where E is the total energy, p is the momentum, c is speed of light. (b) In the lab frame, an utlra-relativistic electron with γ = 100 collides head-on with a photon of energy E. Find the threshold energy E required to...

If energy is kept constant and intensity of photons is increased, will the threshold frequency be lowered? I ask because I'd like to understand this graph - http://www.flickr.com/photos/coachrobbo/3909285882/ "lower intensity same frequency" causes stopping voltage to be lowered, thus...

Sounds ok to me. If I have more than two drinks, I don't drive. When I'm out on a weekend I see far to many people get behind a car when they shouldn't. We also need to make the punishments more severe. I hear of many reports of people with 3-4-5 DUIs still with a license or still driving...

Hello, I regard a proton-proton collision. (Target at rest.) Here accrues a K^{+}(494) -meson. I want to callculate the threshold energy. But I think for callculating the threshold I have to know all participant of the product. Can i assume, that the protons will not be destroyed...

The sound level from a siren emitting sound with a frequency of 2400 Hz is 75.0 dB at a distance of 47.0 m from the siren. Assume that the intensity of that sound obeys the inverse square law. Calculate how far from the siren a person, with a threshold of hearing of 36.0 dB at that frequency...

My textbook says that in the equation β= 10log(I1/I2), I1 in most cases is the threshold of hearing (1.0x10^-12). Just out of curiosity, when is I1 not the threshold of hearing?

Greetings, I have two signals, I need a way of testing whether they go above certain threshold voltages for a period of 0.5 seconds. This must be non programmable. I am a bit stumped o how to do it. I thought of having these signals go into an AND gate and then have that AND gate feed into...

Why does the Vth of MOSFETs depends on Vsb and not Vdb even though MOSFETs are symmetrical devices? Is it a convention to choose Vsb over Vdb or am I missing out on something more fundamental?

Homework Statement A high-energy photon γ1 of energy 261 GeV collides with an infrared photon γ2 of energy 1eV to produce an electron-positron pair via the reaction γ1 + γ2 → e- + e+ The Attempt at a Solution Conservation of momentum: p1 - p2 = (0.5)pe...

Homework Statement Electrons are emitted from a metal as a consequence of their absorption of energy from a light beam. Find the threshold frequency of the metal and the wavelength of emitted electrons. Wavelength of incident light λ = 500 nm Work function of the metal \phi = 2.1 eV Homework...

Homework Statement A thin target of lithium is bombarded by helium nuclei of energy E0. The lithium nuclei are initially at rest in the target but are essentially unbound. When a Helium nucleus enters a lithium nucleus, a nuclear reaction can occur in which the compound necleus splits apart...

Is there fixed data for the threshold frequency of metals? For example, is it possible to find out the threshold frequency of iron or copper? OR does threshold frequency vary so greatly that with 2 blocks of iron, the theshold frequency could differ between them? Depending on the...

Homework Statement Determine the threshold energy for electrons to produce Cerenkov radiation in glass (refractive index n=1.52). The Attempt at a Solution The only equations given in my notes are: cos \theta_{C}=1/\betan for \beta>1/n and...

Homework Statement When a beam if high-energy protons collides with protons at rest in the laboratory, pions are produced by the reaction p + p --> p + p + ∏. Compute the threshold energy of the protons in the beam for this reaction to occur. Homework Equations (mc^2)^2 = E^2 - (pc)^2...

Homework Statement Hi all, I have been trying to go over this problem for sometime now.. yes I have easily browsed over +200 articles, lectures , etc on google. The question is related to delong petit law and wants me to find out the temperature at which it fails i.e when quantum effects...

Homework Statement Determine the threshold frequency of a metal with a work function of 7V Homework Equations Threshold frequency 'f'=W/h where w=work function, h=planck's constant The Attempt at a Solution This is such an easy question, but I am hung up on how to treat a work...

Homework Statement True/False: In the photoelectric effect, the cut-off (threshold) frequency depends on the intensity of incident light. Homework Equations hv = W + 1/2mv^2 v = W/h The Attempt at a Solution The threshold frequency depends on the wavelength of incident light...

hey! Wind turbines have got certain threshold speed of wind (of about 6-7 m/s) which acts as a mechanical resistance to its rotation. Is this mechanical resistance a result of frictional resistance in bearings alone, or it is also a result of its own weight? If yes, approximately how much...

Homework Statement Calculate the threshold ionization intensity for hydrogen gas. The attempt at a solution The way I tried to work it out was to use the field intensity of air which breaks down at, 3x10^6V/m. The ionization potential of oxygen is 13.618ev, 14.534ev for nitrogen and 13.598ev...

Homework Statement A thin target of lithium is bombarded by helium nuclei of energy E0. The lithium nuclei are initially at rest and are essentially unbound for this high-energy collision. A nuclear reaction can occur in which 4He + 7Li → 10B + 1n −2.8 MeV The collision is inelastic, and...

In the paper (AIP Conf. Proc. 810 (2006), 360): Mardari outlines three predictions of quantum self-interference, all of which empirical evidence is presented that appear to refute all three. The implications of the paper is interesting but of these I am particularly interested in the...

Homework Statement We will deal here with a certain identified synapse in the CNS of the mooncalf (Bos lunaris). The post synaptic cell has voltage-sensitive channels like the squid axon-- a rapidly depolarizing, inactivating channel which conducts only sodium ions, and a slowly depolarizing...

Say you were at the very edge of the universe and moving with it at the expansion rate and you look out to the "nothingness" what would you see? I personally think that the "Ganzfield Effect" would take place, when some of your perceptions are shut then your mind compensates. So I was...

Just as a note I am new to these forums and this is my first post after reading for a little while, I have no technical expertise and am a complete layman. So any advice on posting is welcome. From reading threads on these forums discussing properties of black holes and event horizons as I...

I want to know all about nuclear thresholds...where can i learn about them...? (e.g threshold energy and how particles behave under them...different types of threshold energy and their behavior)

I want to know about the thresholds of particles observed when colliding two matter particles together in fermilab or CERN i.e the pion production threshold is 290 MeV, what other thresholds are there? What is the complete list of thresholds according to the energy provided? "Is there a...

Im a little confused about how to calculate threshold energies. The threshold energy is when the energy is as low as it can possibly be and still do what it has to do, yes? So when a neutrino is detected its speed is refracted by water and so it slows down. If at the threshold the neutrino speed...

Homework Statement A surface of a substance has a work function of 2.24 eV. (a) What is the maximum kinetic energy of ejected electrons if the incident radiation is of wavelength 419 nm? eV (b) What is the threshold wavelength for this surface? nm Homework Equations E=hf...

Hi, I noticed such a strange behavior in my code every time I add a threshold: little oscillation around the threshold value itself. For example f(x) = g(x), x > x_c f(x) = 0, x <= x_c \frac{dx}{dt}=f(x) I solve the last equation and I find this oscillation. Can they be removed?

Can someone help me out with this problem(not homework ofcourse).. Find the threshold energy of gamma quantum required to form - an electron-positron pair in the field of a stationary electron; - a pair of pions of opposite signs in the field of a stationary proton.. Thank you for reading

I've heard talk of this safety threshold for ionizing radiation, whereby if the dose is sufficiently low enough, it would produce no harmful side-effects. Can someone explain to me the reasoning behind this? The way I see it, every single ionizing particle that passes through a cell has a...

Hi folks, EM radio signals range in frequencies from a couple Hz up to approximately EHF (30-300GHz)... As we exceed the 300GHz threshold, we begin to approach the infrared section of EM spectrum, and furthermore into the visible light area of the spectrum. My question is, what happens...

First post, after tinkering with electronics so long I just had to join a physics oriented forum. I'm trying to work out how I can get an input voltage to "clip" at a certain level. I start by imagining an ideal diode (no current on reverse bias, infinite current on forward bias). My setup...

Hi everyone, I have a problem with the following equation that is related to Cerenkov counter. You can find it at page 56 of "Introduction of High Energy Physics" by Perkins. The equation is the following: sin ^{2} (\theta _1)=1-\frac{1}{\beta...

Homework Statement At a distance of 30 m the noise from the engine of an jet has an intensity of 130 dB. At this level, you will be in pain and your ears will hurt. That's why this intensity is know as the "pain threshold". How far do you have to be from a jet (total distance), in...

Homework Statement Given the reactions: p + 9 Be --> 10B + "gamma" p + 9 Be --> 9B + 1n p + 9 Be --> 9Be + 1p p + 9 Be --> 8Be + 2H p + 9 Be --> 7Be + 3H p + 9 Be --> 6Li + 4He Calculate: a) Q-value b) kinematic threshold energy of the proton...

What effects do the physical properties (size of atom etc.) of an elemental metal have on the threshold frequency for that metal? I haven't been able to find a correlation between a physical property and the size of the threshold frequency myself; maybe I haven't looked hard enough, or maybe...

What is stack effect in cmos design and how would it affect the threshold voltages?

Homework Statement Calculate the photon energy threshold for the reaction γ + p → p + π. Assume that the initial state proton is stationary. <thats really it> Homework Equations < unknown, but suspects include: standard special relativity equations > -- other useful relations: proton rest...

Homework Statement When a beam of high energy protons collides with protons at rest in the laboratory, neutral pions are produced by the reaction p + p ---> p + p + pi^o. Compute the threshold energy of the protons in the beam for this reaction to occur. Homework Equations The...

Hi, I have Ids vs Vds characteristic curves for a MOSFET at Vgs = 2V and Vgs = 2.5V in both the linear (ohmic) and saturated regions. I wanted to try to figure out the threshold voltage for the MOSFET from this information only. I had two ideas of how to do this, but they differ by a factor...

Light of frequency 1.21e15 Hz illuminates a piece of tin, and the tin emits photoelectrons of maximum kinetic energy 1.96 eV. What is the threshold frequency of the metal? Planck's Constant*Frequency = (Planck's Constant)(Threshold Frequency) + Maximum Kinetic Energy 1.21e15 = (6.63e-34)(x) +...

E(threshold enrgy) = M* − M(squared) −m(squared) divided by 2M Determine the threshold energy for producing a top quark and an anti-top quark when beams of electrons and positrons of equal energy are made to collide head on. What do i sub in where and what do i with M*. Thanks

Homework Statement Out of Sodium (2.75 eV), Cesium (2.14 eV) and Silver (4.73 eV), which metal would be best suited to coat the cathode of the light meter such that it is sensitive to all colors of light? The range of wavelength for visible light is 700 nm to 400 nm. Homework Equations...

If you are told that a silver surface is irradiated with light having a wavelength of 230 nm that causes electrons to be ejected with 77.67 kJ/mol of kinetic energy, how would you find the threshold frequency? I know that threshold frequency = W / h. W is the work function and h is...

An article in the National Geographic states: "According to Berkland, the U.S. Geological Survey said such a theory is ridiculous—the Earth is 82 times more massive than the moon. Though the Earth can trigger quakes on the moon, they said, the moon is too small to trigger any earthquakes."...

At what point should one consider getting professional help for PF addiction?

i am having some trouble understanding the meaning of what a percolation threshold is p_{c}. apparently on triangular lattices a threshold of 0.5 is the result on any sized lattice. however i can definitely think of a way to fill in half the points on a triangle lattice and not have it span...

hi, I have the reaction: (photon) + (proton) ---> (neutron) + (pion+) I have to find the minimum energy of the photon. A first condition can be that total energy of photon and proton has to be at least the mass energy of the output, but I don't think this can be a satisfying solution...