An electron (mass \(m\)) with an initial velocity \(v={ v }_{ 0 }\vec { i } ({ v }_{ 0 }>0) \) is an electric field \(v={ v }_{ 0 }\vec { i } ({ v }_{ 0 }>0)\quad \) its de-Broglie wave-length at time \(t\) is given by

A and B are two metals with threshold frequencies \(1.8\times { 10 }^{ 14 }Hz\)and \(2.2\times { 10 }^{ 14 }Hz\)Two identical photons of energy 0.825 eV each are incident on them. Then photoelectrons are emitted in (take \(h=6.63\times { 10 }^{ -34 }J/s\)

Silver has a work function of 4.7eV when ultraviolet light of wavelength 100 nm is incident upon it, a potential 0f 7.7 is required to stop the photoelectrons from reaching the collector plate.How much potential will be required to stop the photoelectrons when light of wavelength 200 nm is incident upon silver? 

 The wavelength of a KeV photon is \(1.24\times { 10 }^{ -9 }m\). What is the frequency of 1 MeV photon?

If v is frequency, \(\lambda \) is the wavelength and \(\overline { v } \) is the wave number then the energy of a photon can be represented by 

Two metals X and Y have work functions 2eV and 5eV respectively. Which metal will emit electrons when it is radiated with light of wavelength 400nm and why?

The work function of caesium is 2.14eV. Find (a)the threshold frequency for caesium and

(ii)the wavelength of the incident light if the photocurrent is brought to zero by a stopping potential of 0.60eV.

A monoenergetic electron beam with electron speed of

5.20X10⁶ms^-1 is subject to a magnetic field of 1.30X10^-4T normal to the beam velocity. What is the radius of the electron equals 1.76X10¹¹C kg^-1.

(i) For what kinetic energy of a neutron will associated de Broglie wavelength be 1.40 x 10^-10m?
(ii) Also find the de-Broglie wavelength of a neutron in thermal equilibrium with matter,having an average kinetic energy of (3/2) kT and temperature is 300 K.

The ground state energy of hydrogen atom is -13.6 eV. The photon emitted during the transition of electron from n=2 to n=1 state is incident on a photosensitive material of unknown work function. The photoelectrons are emitted from the materials with a maximum kinetic energy of 8 eV. Calculate the threshold wavelength of the material used.

Find the frequency of light which ejects electrons from a metal surface fully stopped by a potential of 3 V.The photoelectric effect begins in this metal at frequency of 6*\({ 10 }^{ 14 }{ sec }^{ -1 }\) the work function for this metal.

Calculate the wavelength associated with an electron subjected to potential difference of 1.25 K.V.

What are the energies of photons at the (a)Violet, and (b) red ends of the visible spectrum  ? The wavelength of light is about 390 nm for violet and about 760 nm for red.

Find the difference of kinetic energies of photoelectrons emitted from a surface by light of wavelengths \(2500\mathring { A } and \ 5000\mathring { A } \)

Consider a thin target \(({ 10 }^{ -2 }\)m square, \({ 10 }^{ -3 }\)m thickness) of sodium, which produces a photocurrent of \(100\mu A\) when a light of intensity 100w/\({ m }^{ 2 }\) ( \((\lambda =660nm)\) falls on it. Find the probability that a photoelectron is produced when a photon strikes a sodium atom.[Take density of Na = 0.97 kg/\({ m }^{ 3 }\)

What is the photoelectric effect? Explain experimentally the variation of photoelectric current with (i) the intensity of the incident light (ii) the potential difference between the plates and (iii) the frequency of the incident light and hence state the laws of photoelectric emission.

The photoelectric effect is a phenomenon of emission of electrons from the surface of a metal when the light of suitable frequency falls on it.
If light of frequency v falls on a photosensitive surface of work function increases or work function then the maximum kinetic energy of photoelectric emitted is given by Einstein's photoelectric equation.
\({ (KE) }_{ max }=\frac { 1 }{ 2 } { { mv }^{ 2 } }_{ max }=hv-{ { \phi }_{ 0 } }\)
The value \({ (KE) }_{ max }\) will increase if the energy of the incident light(hv) increases or work function \({ { \phi }_{ 0 } }\) is decreased.
Read above passage and answer the following questions:
(i) Why can visible light not eject photoelectrons from every metal surface?
(ii) Light of frequency \(7.21\times { 10 }^{ 14 }Hz\) is incident on a metal surface.Electrons with a maximum speed of \(6.0\times { 10 }^{ 5 }{ ms }^{ -1 }\) are ejected from the surface. What is the threshold frequency for photo emission of electrons?\(h=6.63\times { 10 }^{ -34 }Js;\ { m }_{ e }=9.1\times { 10 }^{ -31 }kg\)
(iii) What do you learn basically from the above study? 

Neha's brother was riding the bike on the highway and she was sitting behind him. While sitting, at a place traffic signal turned red from green and her brother continued riding without noticing the signal change. Neha observed the whole situation and asked her brother to stop. Her brother felt happy on his sister's intelligence.
Read above passage and answer the following questions:
(i) Why Neha's brother became happy? What kind of value is expressed by Neha?
(ii) What are the principles that are used in maintaining traffic signals?
(iii) What is the leading physical quantity i8n the process? Write an equation for the speed of the photoelectron.