As the name suggests Dual Nature of Matter and Radiation chapter deals with the duality in the nature of matter, namely particle nature and a wave nature. Various experiments by various scientists were done to prove it. For example, light behaves both as a wave and as a particle. If you are observing phenomenon like the interference, diffraction or reflection, you will find that light behaves as a wave. However, if you are looking at phenomena like the photoelectric effect, you will find that light behaves as a particle. You must have heard about solar energy in your earlier classes and how it can be a good alternative to the non-renewable sources of energy. We can use solar energy as a source of electricity using solar panels. The solar panel has solar cells (semiconductors like Si and Ge) and when photons hit the solar cells the electrons get excited and due to their movement electric current is produced. So here we got to know that light constitutes of photons or in other words light contains particles which are a packet of energy.
But light does not only shows particle nature it also shows the wave nature and you will get to know about it by various experiments. I hope now you understand why this chapter’s name is Dual Nature of Matter and Radiation.
Dual Nature of Matter and Radiation is one of the most important chapters from modern physics while preparing for all competitive exam because it helps you to understand the dual nature of matter. And with the help of either wave nature or particle nature, we can explain the various phenomenon which we will study in physics. This is easy to understand and a high scoring topic. The Concept of Dual Nature of Matter and Radiation and other chapters of physics are mixed in miscellaneous questions which are asked in various competitive exams.
So we will discuss step by step about important topics from this chapter followed by an overview of this chapter. Then we will understand important formulas from this chapter. Remembering these formulas will increase your speed while question-solving.
Dual nature of radiation,
photoelectric effect,
Hertz and Lenard's observations,
Einstein’s photoelectric equation,
Matter-wave: the wave nature of particles,
De Broglie relation, Davisson and Germer experiment.
The energy of a photon-
Einstein's Photoelectric Equation=
De - Broglie wavelength-
For Dual Nature of Matter and Radiation, chapter concepts in NCERT are enough but you will have to practice lots of questions including previous year questions and you can follow other standard books available for competitive exam preparation like Concepts of Physics (H. C. Verma) and Understanding Physics by D. C. Pandey (Arihant Publications).
Chapters No. |
Chapters Name |
Chapter 1 |
|
Chapter 2 |
|
Chapter 3 |
|
Chapter 4 |
|
Chapter 5 |
|
Chapter 6 |
|
Chapter 7 |
|
Chapter 8 |
|
Chapter 9 |
|
Chapter 10 |
|
Chapter 11 |
|
Chapter 12 |
|
Chapter 13 |
|
Chapter 14 |
|
Chapter 15 |
|
Chapter 16 |
|
Chapter 18 |
|
Chapter 19 |
|
Chapter 20 |
|
Chapter 21 |
According to Einstein’s photoelectric equation, the plot of the kinetic energy of the emitted photo electrons from a metal the frequency, of the incident radiation gives a straight line whose slope
Option 1)
depends on the nature of the metal used |
Option 2)
depends on the intensity of the radiation |
Option 3)
depends both on the intensity of the radiation and the metal used |
Option 4)
is the same for all metals and independent of the intensity of the radiation. |
Question is based on the following paragraph.
Wave property of electrons implies that they will show diffraction effects. Davisson and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively (see figure).
Question : In an experiment, electrons are made to pass through a narrow slit of width comparable to their de Broglie wavelength. They are detected on a screen at a distance
from the slit.
Which of the following graphs can be expected to represent the number of electrons detected as a function of the detector position
(
= 0 corresponds to the middle of the slit)?
Option 1)
|
Option 2)
|
Option 3)
|
Option 4)
|
Question is based on the following paragraph.
Wave property of electrons implies that they will show diffraction effects. Davisson and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively (see figure).
Question : If a strong diffraction peak is observed when electrons are incident at an angle from the normal to the crystal planes with distance
between them (see figure), de Broglie wavelength
of electrons can be calculated by the relationship (
is an integer )
Option 1)
|
Option 2)
|
Option 3)
|
Option 4)
|