1. e.mail: iitd.arvind@gmail.com kumara@nitj.ac.in
B. Tech Physics PHX(101) By
Dr. Arvind Kumar
Physics Department
NIT Jalandhar
e.mail:
Website:

2. Contents of Course: (For Applied Physics-I)
I. Quantum Theory
II. Electromagnetism
Theory of Relativity
IV . Crystal Structures
V. Mechanical Properties
VI. Thermal & Statistical Physics
Total Marks = 100
First Minor = 20 Marks
2nd Minor = 20 Marks
Major = 50 Marks
Internal Assessment = 10 Marks

3. Section I Quantum Mechanics Lecture 1.1
Books:(1) A. Beiser, “Concepts of Modem Physics”,
McGraw Hill
(2) K S Krane, “Modern Physics”, John Wiely & Sons, Inc.,
3rd Ed. (2011).
(3) H K Malik & A K Malik, “Engineering Physics”, McGraw
Hill Education, 2nd Ed. (2017).

4. Origin of Quantum Physics
Upto the end of 19th Century Physics was essentially
classical physics: Newtonian Physics, Maxwell
electromagnetic theory, thermodynamics.
Challenge to classical physics in beginning of 20th
century
Relativistic domain: Galilean theory fails;
Einstein theory of relativity came into picture in 1905.
Microscopic domain: phenomenon observed at
atomic-subatomic dimensions observed due to
advancement in experimental technology

5. Classically Wave & Particle two different entities
Classically light is a wave.
Interference, diffraction, polarization explained by
wave nature of light
But Blackbody radiations, Photoelectric effect ,
Compton effect need quantization of light

6. Max Planck idea (in 1900): Quantization of energy exchange between radiations and matter take place in discrete amount (in integer multiple of hν). This idea explained blackbody radiation spectra.
Planck’s law

7. threshold frequency is made to fall on it. Experimental observations:
Photoelectric effect
Instantaneous emission of bound electrons from the
surface of metal when light of frequency greater than
threshold frequency is made to fall on it.
Experimental observations:
No matter what is the intensity
of incident radiations, the electric
current will be observed
only when the incident radiations have
frequency greater than some threshold frequency.
This threshold frequency vary from metal to metal.

8. Once the frequency of incident radiations is greater
than threshold frequency, the current will be
observed instantaneously whether intensity is low
or high.
If the positive potential at anode is increased then
more electrons will be attracted and current will
increase upto a saturation value. If the intensity
of light is increased, then the value of current is also
observed to increase.

9. When the anode is put at negative potential, then electrons will be repelled by it and only those electrons will contribute to current which have sufficient kinetic energy to overcome the potential energy eV. The negative potential at which no current is observed is known stopping potential Vs

10. If light beams of different frequencies are used, then as shown in fig, the value of stopping
potential will be large for the higher frequency.

11. Explanation:
Classical Physics View
Photoelectric effect should depend upon intensity
of radiations instead of frequency of radiations.
Photoelectric effect should not be an
instantaneous process.
Above classical explanation does not agree with the
Experimental results and hence, rejected.

12. Quantum Physics View
Einstein postulated that the light is made up
of discrete packet of energy. These packets of
energy are known as photons.
Only those photons will be able to eject the
electron which possess the energy greater than
The work function of metal.

13. The work function of a metal surface is the minimum energy which the incident photon should possess to overcome the electron’s binding energy in the metal.
The work function is the characteristic of metal and vary from one metal to other.
Kinetic energy of ejected electrons will be

14. Using
We can write or

15. List of Few Metals with Work Function
Exercise: Photoelectric effect is possible only with
bound electrons. Photons cannot
Impart whole of its energy to free electron.
Hint: Use total momentum and energy conservation
law