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. 


Correct option is


Kinetic energy of photoelectrons emitted = hv – hv0 = h(v – v0









What is the wavelength of the light emitted when the electron in a hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2? What is the colour corresponding to this wavelength? (Rydberg constant = 109,677 cm–1  


A certain particle carries 2.5 × 10–16 C of static electric charge. Calculate the number of electrons present in it.


An ion with mass number 37 possesses one unit of negative charge. If the ion contains 11.1% more neutrons then the electrons, find the symbol of the ion.    


An ion with mass number 56 contains 3 units of positive charge and 30.4% more neutrons than electrons. Assign the symbol to this ion.


Nitrogen laser produces a radiation at a wavelength of 337.1 nm. If the number of photons emitted is 5.6 × 1024, calculate the power of this laser.


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.


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?