The first scientist to measure the charge to mass ratio of the electron was
J J Thomson
J J Thomson
Crystal diffraction experiments can be performed using X-rays or electron accelerated through appropriate voltage. Which probe, an X-ray photon or the electron, has greater energy? Take the wavelength of either probe equal to 1 Å, which is of the order of interatomic spacing in the crystal lattice. Mass of electron is .
Obtain de-Broglie wavelength of a neutron of kinetic energy 150 eV. As we have seen in last example, an electron beam of 150 eV energy is suitable for crystal diffraction experiments. Would a neutron beam of the same energy by equally? Explain. The mass of neutron is .
X-rays of wavelength 0.82 Å fall on a metal plate. Find the smallest wavelength associated with the emitted photoelectrons. The work function of the metal is zero.
Obtain the de-Broglie wavelength associated with thermal neutrons at room temperature (27o C). hence explain why a fast neutron beam needs to be thermalised with the environment before it can be used for neutron diffraction experiments. The mass of neutron is and the Boltzmann constant .
Calculate the de-Broglie wavelength of an electronic energy 100 eV.
An electron microscope uses electrons accelerated through 50 kV. Find the de-Broglie wavelength of these electrons. If other factors like numerical aperture etc. are roughly the same, how does the resolving power of an electron microscope compare with that of an optical microscope which uses variable light?
The force exerted by a magnetic field on a charged particle is independent of the
The monoenergetic electron beam electron speed of is subjected to a magnetic field of normal to the beam velocity. What is the radius of the circular path traced by the beam? Given e/m forelectron .
Two parallel plates are placed 5 cm apart in an evacuated tube and a potential difference of 200 V is applied across them? What is the force experienced by an electron at rest in the region between the plates?
In Thomson’s experiment for determining , the potential difference between the cathode and the anode (in the accelerating column) is the same as that between the deflecting plates (in the region of crossed fields). If the potential difference is doubled, by what factor should the magnetic field be increased to ensure that the electron beam remains undeflected?