Advertisements
Advertisements
प्रश्न
Is p − E/c valid for electrons?
Advertisements
उत्तर
From Einstein's mass- energy equation,
`E = mc^2`
⇒ `E = (m_0c^2)/sqrt(1-v^2/c^2)`
Relativistic momentum ,
`p = mv`
⇒ `p = (m_0c^2)/sqrt(1-v^2/c^2)`
Combining the above equations, we get :
`E^2 = m_0^2c^4 + p^2c^2`
From the above equation, it is clear that for p = E/c to be valid, the rest mass of the body should be zero. As electrons do not have zero rest mass, this equation is not valid for electrons.
APPEARS IN
संबंधित प्रश्न
In an experiment on the photoelectric effect, the slope of the cut-off voltage versus the frequency of incident light is found to be 4.12 × 10−15 Vs. Calculate the value of Planck’s constant.
In an accelerator experiment on high-energy collisions of electrons with positrons, a certain event is interpreted as annihilation of an electron-positron pair of total energy 10.2 BeV into two γ-rays of equal energy. What is the wavelength associated with each γ-ray? (1BeV = 109 eV)
Write Einstein’s photoelectric equation?
Briefly explain the three observed features which can be explained by Einstein’s photoelectric equation.
A small metal plate (work function φ) is kept at a distance d from a singly-ionised, fixed ion. A monochromatic light beam is incident on the metal plate and photoelectrons are emitted. Find the maximum wavelength of the light beam, so that some of the photoelectrons may go round the ion along a circle.
In a photoelectric experiment, the collector plate is at 2.0 V with respect to the emitter plate made of copper (φ = 4.5 eV). The emitter is illuminated by a source of monochromatic light of wavelength 200 nm. Find the minimum and maximum kinetic energy of the photoelectrons reaching the collector.
Use Einstein’s photoelectric equation to show how from this graph,
(i) Threshold frequency, and (ii) Planck’s constant can be determined.
The wavelength of a photon needed to remove a proton from a nucleus which is bound to the nucleus with 1 MeV energy is nearly ______.
- In the explanation of photo electric effect, we assume one photon of frequency ν collides with an electron and transfers its energy. This leads to the equation for the maximum energy Emax of the emitted electron as Emax = hν – φ0 where φ0 is the work function of the metal. If an electron absorbs 2 photons (each of frequency ν) what will be the maximum energy for the emitted electron?
- Why is this fact (two photon absorption) not taken into consideration in our discussion of the stopping potential?
Radiation of frequency 1015 Hz is incident on three photosensitive surfaces A, B and C. Following observations are recorded:
Surface A: no photoemission occurs
Surface B: photoemission occurs but the photoelectrons have zero kinetic energy.
Surface C: photo emission occurs and photoelectrons have some kinetic energy.
Using Einstein’s photo-electric equation, explain the three observations.
Which observation could classical wave theory not explain?
Which feature of photoelectric emission could classical wave theory not explain?
Einstein proposed that light energy is absorbed in discrete packets called what?
Which equation gives the energy of one photon?
In \[E=h\nu\], what does \[\nu\] represent?
Which expression gives the maximum kinetic energy of emitted photoelectrons?
What does \[\phi_0\] represent in Einstein’s photoelectric equation?
If the frequency is above the threshold, how does greater intensity affect the number of electrons emitted?
