Home
Class 12
PHYSICS
Find the threshold wavelengths for photo...

Find the threshold wavelengths for photoelectric effect from a copper surface, a sodium surface and a cesium surface. The work functions of these metals are 4.5 e V, 2.3 eV and 1.9 eV respectively.

Text Solution

Verified by Experts

If ` lambda_0` be the threshold wavelength and `varphi` be the
work function,
` ( lambda_0)= hc/varphi`
`= 1242 eV nm/varphi.`
` For copper, lambda_0=(1242 e V nm/ 4.5 e V) = 276 nm. `
` For sodium, lambda_0= (1242e V nm/ 2.3 e V) = 540nm.`
` For cesium, lambda_0 = (1242 e V nm/ 1.9 e V) = 654 nm.`
Promotional Banner

Topper's Solved these Questions

  • PHOTO ELECTRIC EFFECT AND WAVE PARTICLE DUALITY

    HC VERMA|Exercise Short Answer|13 Videos

  • PHOTO ELECTRIC EFFECT AND WAVE PARTICLE DUALITY

    HC VERMA|Exercise Objective 1|14 Videos

  • PHOTO ELECTRIC EFFECT AND WAVE PARTICLE DUALITY

    HC VERMA|Exercise Worked Out Examples|4 Videos

  • PERMANENT MAGNETS

    HC VERMA|Exercise Exercises|25 Videos

  • PHOTOMETRY

    HC VERMA|Exercise Exercises|16 Videos

Similar Questions

Explore conceptually related problems

When the energy of the incident radiation is increased by 20% ,the kinetic a metal surface increased from 0.5 eV to 0.8 eV.The work function of the metal is …..

What will be maximum value of wavelength by which photo-electric emission can be obtained on metal surface with work function of 3.2 eV? ( h=6.625xx10^(-34) Js)

Light of intensity 10^(-5) W m^(-2) falls on a sodium photo-cell of surface area 2 cm^(2) . Assuming that the top 5 layers of sodium absorb the incident energy, estimate time required for photoelectric emission in the wave-picture of radiation. The work function for the metal is given to be about 2 eV. What is the implication of your answer?

Consider a 20 W bulb emitting light of wavelength 5000 Å and shining on a metal surface kept at a distance 2m.Assume that the metal surface has work function of 2eV and that each atom on the metal surface can be treated as a circular disk of radius 1.5 Å. (i)Estimate no. of photons emitted by the bulb per second.[Assume no other losses] (ii)Will much time would be required by the atomic disk to receive energy equal to work function (2eV)? (iv)How many photons would atomic disk receive within time duration calculated in (iii)above? (v) Can you explain how photoelectric effect was observed instantaneously?

Photoelectric effect experiments are performed using three different metal plates p,q and r having work function phi_(p) = 2.0 eV, phi_(e) = 2.5 eV and phi_(r) = 3.0 eV respectively A light beam containing wavelength of 550nm , 450 nm and 350nm with equal intensities illuminates each of the plates . The correct I -V graph for the experiment is [Take hc = 1240 eV nm]

A metallic surface is illuminated alternatively with light of wavelenghts 3000 Å and 6000 Å . It is observed that the maximum speeds of the photoelectrons under these illuminations are in the ratio 3 : 1 . Calculate the work function of the metal and the maximum speed of the photoelectrons in two cases.

The maximum kinetic energy of photoelectrons emitted from a surface when photons of energy 6 eV fall on it is 4 eV . The stopping potential , in volt is

The threshold frequency of cesium is 5.16 xx 10^(14) Hz. Then its work-function is _____ eV.

In photoelectric effect threshold wavelength of sodium is 5000Å .Find its work function. [ h=6.6xx10^(-34)Js,c=3xx10^(8)m//s,1eV=1.6xx10^(-19)Js]

The ejection of the photoelectron from the silver metal in the photoelectric effect experiment can be stopped by applying the voltage of 0.35 eV with the radiation 256.7 nm is used .Calculated the work function silver metal.