photo electric effect

Yellow light of 557 nm wavelength is incident on a cesium surface. It is found that no photo electrons flow in the circuit when the cathode-anode voltage drops below 0.25V. Then the threshold wavelength for photo electric effect from cesium is

Given figure shows few data points in a photo electric effect experiment for a certain metal. The minimum energy for ejection of electron from its surface is ejection of electron from its surface is : (Plancks constant h = 6.62xx10^(-34) Js )

In photo electric effect, if the energy required to over come the attractive forces on the electron (work function) of Li, Na and Rb are 2.41eV, 2.3eV and 2.09eV respectively, the work function of ''K'' could approximately by in eV

The photoelectric threshold of the photo electric effect of a certain metal is 2750 A^(@) . Find (i) The work function of emission of an electron from this metal, (ii) Maximum kinetic energy of these electrons. (iii) The maximum velocity of the electrons ejected from the metal by light with a wavelength 1800 A^(@) .

In a photo electric effects set-up, a point source of light of poewer 3.2xx10^(-3) W emits mono energetic photons of energy 5.0 Ev. The source is located at a distance of 0.8m from the centre of a stationary metallic sphere of work function 3.0 Ev & of radius 8.0xx10^(6) m. The efficiency of photo electric emission is one of every 10^(6) incident photons. Assume that the sphere is isolated and initially neutral, and that photo electrons are instantly swept awy after emission. (a) Calculate the number of photo electrons emitted.per second. (b) Find the ratio of the wavelength of incident light to the de-Broglie wave length of the fastest photo electrons emitted. ltbr. (c) It is observed that the photo electron emission stops ata certain time tafter the light source is switched on. Why ? (d) Evaluate the time t.

Which of the following is correct regarding Einstein photo-electric effect equation? (i) The equation is hv =hv_(0) + K_(max) =hv_(0)+ eV_(s) (ii) The variation of V_(s) with v is (iii) The variation of photo-current versus applied potential (iv)

In an experiment on the photo-electric effect Singly ionized helium is excited electronically to different energy levels. The light emitted by ionised helium is incident on photo-electric plate in a photocell. When helium is excited to fourth energy level, then the observed stopping potential of the photocell is found to be five times the stopping potential measured when the photoelectrons are produced by using light emitted by hydrogen atom, excited to the third energy level. Determine the work function of the material of the photo-electric plate.

Which of the following is correct regarding photo-electric effect? (i) The photo-electric effect takes place if lambda le lambda_(0) or upsilon ge upsilon_(0) . maximum K.E. of photo-electron K_(max) =hv=(hc)/(lambda) Einstein photo-electric effect equation hv=hv_(0) + K_(max) (ii) The maximum K.E. of electron or stopping potential V_(s)(K_(max) =eV_(s)) for a given metal depends only on frequency or wavelength of incident light and not on its intensity (iii) The saturation current (i =ne, n: number of photo-electrons ejected per unit time) depends on intensity and not frequency (iv) Normally it is assumed that one photon eject one electron. Practically several incident photons eject one electron. If quantum efficiency is given {"Quantum efficiency" =("Number of electrons ejected")/("Number of photons incident")} Number of electrons ejected must be calculated must be calculated and then calculate saturation current