Define the term:
(a) (i)Work function
(ii) threshold frequency and
(iii) stopping potential with reference to photoelectric effect
(b) Calculate the maximum kinetic energy of electrons emitted from a photosensitive surface of work function 3.2 eV for the incident radiation of wavelength 300 nm.

The energy flux of sunlight reaching the surface of the earth is \(1.388\times{ 10 }^{ 3 }w/{ m }^{ 2 }\). How many photons (nearly) per square metre are incident on the Earth per second? Assume that the photons in the sunlight have an average wavelength of 550 nm.

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 an MW transmitter of 10 kW power emitting radio waves of wavelength 500 m.
(b) The number of photons entering the pupil of our eye per second corresponding to the minimum intensity of while light that we humans can perceive (\(\sim \)\({ (10 }^{ -10 }Wm^{ -2 })\). Take the area of the pupil to be white light to be about 0.4 cm² and the average frequency of white light to be about 6 x 10¹⁴ Hz.

Answer the following question.
(a) Quarks inside protons and neutrons are thought to carry fractional charges \(\left( +\frac { 2 }{ 3 } e,-\frac { 1 }{ 3 } e \right) .\) Why do they not show up in Millikan's oil drop experiment?
(b) What is so special about the combination elm? Why do we not simply talk of e and \(m\) specially?
(c) Why should gases be insulators at ordinary pressure and start conducting at very low pressure.
(d) Every metal has a definite work function, Why do photoelectrons not come out all with same energy if incident radiations is monochromatic?Why is there an energy distribution of photoelectrons?
(e) The energy and momentum of an electron are related to the frequency and wavelength of the associated matter wave by the relations : \(E=hv,p=\frac { h }{ \lambda } \)
But while the value of  \(\lambda \) is physically significant, the value of \(v\) (and therefore the value of the phase speed \(v\lambda \)) has no physical significance. Why?

Two particles A and B of de-Broglie wavelength \({ \lambda }_{ 1 } \ and \ { \lambda }_{ 2 }\) combine to form a particle C. The process conserves momentum. Find the de-Broglie wavelength of the particle C.(The motion is one dimensional).

The electric field associated with a monochromatic beam of light becomes zero, \(2.4\times { 10 }^{ 15 }\) times per second. Find the maximum kinetic energy of the photoelectrons when this light falls on a metal surface whose work function is 2.0eV, h=\(6.63\times { 10 }^{ -34 }Js\)

The minimum light intensity that can be perceived by the eye is about \({ 10 }^{ -10 }{ Wm }^{ -2 }\)Find the number of photons of wavelength \(5.84\times { 10 }^{ -7 }m\)that must enter the pupil, of area \({ 10 }^{ -4 }{ m }^{ 2 }{ s }^{ -1 }\) for vision.

The de-Broglie wavelength associated with a material particle when it is accelerated through a potential difference of 150 V is \(1\mathring { A } \)What will be the de-Broglie wavelength associated with the same particle when it is accelerated through a potential difference of 1350 V?

The wavelength of a photon is \(1.4\mathring { A } \) .It collides with an electron. Its wavelength after collision is \(4\mathring { A } \) . Calaculate the energy of scattered electron.

Calculate packing fraction of \(\alpha -particle\) from the following data:
\({ m }_{ \alpha }=4.0028a.m.u\)
\( { m }_{ p }=1.00758a.m.u.\)
\( { m }_{ n }=1.00897a.m.u.\)

The binding energies per nucleon for deuteron and helium are 1.1 MeV and 7.0 MeV respectively. What would be the energy released when two deuterons fuse to form a helium nucleus?

M1 and M2 represent the masses of \(_{ 10 }{ { Ne }^{ 20 } }\)nucleus and \(_{ 20 }{ { Ca }^{ 40 } }\) nucleus respectively. State whether M2=2M1 or M2>2M1 or M2<2M1

In an experiment on photoelectric effect, the slope of the cut off voltage versus frequency of incident light is found to be \(4.12\times { 10 }^{ -15 }Vs\).  Calculate the value of Plank's constant.

A 100W sodium lamp radiates energy uniformly in all directions.The lamp is located at the centre of a large sphere that absorbs all the sodium light which is incident on it.The wavelength of the sodium light is 589nm.
(a) What is energy associated per photon with the sodium light?
(b) At what rate are the photons delivered to the sphere?