To which orbit the electron in the hydrogen atom will jump after absorbing 1.94× 10–18 J of energy? 


Correct option is

n = 3


Energy of electron is the nth orbit of H-atom is given by 


After absorbing 1.94 × 10–8 J of energy, the energy of the electron will be   




Thus, the electron will jump to the third orbit. 



The angular momentum of an electron in Bohr’s orbital of hydrogen atom is 4.22× 10–34 kg m2s–1. Calculate the wavelength of the spectral line when the electron falls from this level to the next lower level.    


With what velocity must an electron travel so that its momentum is equal to that of a photon of wavelength 560 nm?


If uncertainties in the measurement of position and momentum of an electron are found to be equal in magnitude, what is the uncertainty in the measurement of velocity of the electron? Comment on the result obtained.



When a certain metal was irradiated with a light of frequency

3.2 × 1016 Hz, the photo-electrons had twice the kinetic energy as emitted when the same metal was irradiated with light of frequency 2.0 × 1016 Hz. Calculate the threshold frequency (v0) of the metal. 


A laser emits monochromatic radiation of wavelength 663 nm. If it emits 1015quanta per second per square meter, calculate the power output of the laser in joule per square meter per second.  


An electron in a certainty Bohr orbit has velocity 1/275 of the velocity of light. In which orbit the electron is revolving?


A bulb emits light of wavelength 4500 Å. The bulb is rated as 150 watt and 8% of the energy is emitted as light. How many photons are emitted by the bulb per second?


Find the velocity (in ms–1) of electron in first Bohr orbit of radius a0. Also find the de Broglie wavelength (in m). Find the orbital angular momentum of 2porbital of hydrogen atom in units of h/2π.


An electron in a hydrogen atom in the ground state absorbs energy equal to 1.5 time the minimum energy required to remove the electron from the hydrogen atom. Calculate the wavelength of the electron emitted.  


Find out the number of waves made by a Bohr electron in its 3rd orbit.