X-rays can be diffracted from crystals like the diffraction of light from a grating. The crystal grating for X-rays has a grasting element  


Correct option is

Equal to the distance between any two nearest atoms 

The correct answer is (a) because a crystal acts as a ‘natural grating’ forX-rays as the distance between two neighbouring atoms in a crystal is of the order of the wavelength of X-rays, namely, about 1 Å.



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?   


The first scientist to measure the charge to mass ratio of the electron was


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?


The minimum wavelength of X-rays emitted from an X-ray tube operating at a voltage of 104 volts is roughly equal to  


The energy in monochromatic X-rays of wavelength 1 Å is roughly equal to


What is the unit of Planck’s constant?


What are the dimensions of Planck’s constant?


An X-rays tube produces X-rays whose shortest wavelength is 0.2475 Å. The operating voltage of the tube must be   


In the continuous part of the spectrum of X-rays the limiting frequency is