X-ray tube produces a continuous spectrum of radiation with its short wavelength end at . Å. What is the maximum energy of a photon in the radiation? (b) From your answer to (a), guess what order of accelerating voltage (for electrons) is required in such a tube?
. 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 . BeV into two " -rays of equal energy. What is the wavelength associated with each " -ray?
(1BeV = eV) . Estimating the following two numbers should be interesting. The first number will tell you why radio engineers do not need to worry much about photons! The second number tells you why our eye can never ‘count photons’, even in barely detectable light.
(a) The number of photons emitted per second by a Medium wave transmitter of kW power, emitting radiowaves of wavelength m. (b) The number of photons entering the pupil of our eye per second corresponding to the minimum intensity of white light that we humans can perceive ( – W m – ). Take the area of the pupil to be about . cm , and the average frequency of white light to be about × Hz.
. Ultraviolet light of wavelength Å from a W mercury source irradiates a photo-cell made of molybdenum metal. If the stopping potential is – . V, estimate the work function of the metal.
How would the photo-cell respond to a high intensity ( W m – ) red light of wavelength Å produced by a He-Ne laser? . Monochromatic radiation of wavelength . nm (1nm = – m) from a neon lamp irradiates photosensitive material made of caesium on tungsten.
The stopping voltage is measured to be . V. The source is replaced by an iron source and its . nm line irradiates the same photo-cell.
Predict the new stopping voltage. . A mercury lamp is a convenient