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Chapter 11 – Dual Nature of Radiation and Matter

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:

Introduction

To understand the nature of Radiation and Matter, you will first have to understand the duality of wave and particle nature. With the discovery of cathode rays, the rays were considered to be fast-moving negatively charged particles. With further advancements, Einstein photoelectric equation, where he explained the photoelectric effect with the energy quantum and charge being moving in discrete units called quanta of energy which represented the particle nature.

Few properties of photoelectric were not explained in the particle theory, so de Broglie presented a bold hypothesis that there is symmetry in nature and proposed wave-particle duality of matter. They were later verified by the Davisson and Germer Experiment, and the wave nature of electrons was confirmed and accepted. With this article, you will understand concepts like the Photoelectric effect and the dual nature of Radiation and Matter. These notes with MSVgo video library can help you revise a topic completely.

You know that metals contain free electrons which are required for conductivity. Still, these free electrons do not leave the metal surface as free electrons being negatively charged particles when leaving the surface, the metal surface acquires a positive charge and attracts back the electrons. To overcome this attractive pull minimum energy is required by an electron to leave the metal surface called the work function of the metal. It is denoted by 0 and measured in eV( electron-volt). For electron emission, this minimum energy required can be supplied to the free electrons by these methods – Thermionic emission, Field emission, Photoelectric emission.

The phenomena of electron emission from the metal surface, when the light of sufficient frequency (threshold frequency) falls on the emitter surface is called the photoelectric effect. Found in 1887, by Heinrich Hertz during his experimental study of the photoelectric effect, he observed that when the emitter plate was illuminated by ultraviolet light from an arc lamp, high voltage sparks were produced across the detector. Further, after the discovery of electrons, it was evident that incident light falling on the surface causes electrons to be emitted from the emitter surface, the intensity of light required to each surface is different. The metals which emit electrons when illuminated by light were called photosensitive substances, and the electrons were called photoelectrons.

The following experiment was conducted to study the photoelectric effect. The arrangement consists of an evacuated tube, a photosensitive (emitter) plate and another metal plate. Monochromatic light of short wavelength is made to fall on the emitter plate through a window. As light falls, the emitter plate emits electrons which are collected by the metal plate (collector), and an electric field is created through the battery. As the battery maintains the potential difference between the plates, the collector plate can be held at a desired positive or negative potential with respect to the emitter plate. When the collector plate is positive compared to the emitter plate, the electrons get attracted towards it; this causes electron emission. This arrangement is used to study the variation of photocurrent with

  • Intensity of Radiation
  • Frequency of incident radiation
  • Potential difference between the plates A and C
  • Nature of the material of collector plate

Keeping the frequency of incident radiation and accelerating potential is fixed. By varying the intensity of light, the change in the resulting photoelectric current is observed. Electron emission increases linearly with the intensity of the incident light, which implies that the number of photoelectrons emitted per second is directly proportional to the intensity of incident radiation.

While keeping the emitter plate at positive accelerating potential with respect to a collector plate, and illuminating the collector plate with the light of fixed frequency and fixed intensity we observe that on increasing the accelerating potential (positive) the photoelectric current increases. If we increase the positive potential of the emitter plate further, photocurrent will not increase. This maximum limit is known as saturation current.

Now, applying negative (retarding) potential to the emitter plate, the electrons are repelled, and most energetic are only able to reach the collector plate. The photocurrent decreases rapidly as until it drops to zero at a critical value of negative potential V0 on the emitter plate. This minimum negative potential V0 is called cut-off or stopping potential.

Now, on varying the intensity of Radiation, it is found that the saturation current increases with increased intensity. Thus, more numbers of electrons are emitted per second proportional to intensity.

To study the variation between the incident radiation frequency and the stopping potential V0, we fix the intensity of light at various frequencies and study the variation of photocurrent with collector plate potential. On observation, we get the energy of the emitted electrons depending on the frequency of the incident radiation. For higher frequencies of incident radiation, the stopping potential is more harmful.

Albert Einstein, in 1905, presented a new picture of Electromagnetic Radiation of the photoelectric effect. Instead of continuous absorption of energy, radiation energy is built up discrete units called quanta of the energy of Radiation. Each quantum of energy has the energy of hv, where h is Planck’s constant and v is the frequency of light.

Kmax=hv-0 1.

When the quantum of energy exceeds the minimum energy, the minimum energy needed for the electrons to escape from the metal surface ( work function0), the electron is emitted with maximum kinetic energy. Eqn. 1 is known as Einstein’s Photoelectric Equation.

Wave nature is shown by many phenomena in physics, i.e. interference, diffraction and polarisation. Whereas phenomenons like the photoelectric effect, Compton effect which involve Radiation, energy transfer is explained based on the transfer of photons.

De-Broglie presented a hypothesis that moving particles display wave-like properties under suitable conditions. The waves associated with moving particles were named as de Broglie waves. The wavelength associated with the momentum is given as 

=hp=hmv 2.

The dual nature of Radiation and matter is inherently present in the de Broglie equation as the wave concept is represented by and particle nature is represented by momentum p. m is the mass of the matter. De Broglie wavelength is not evident for the heavier particles as they become very small.

This matter-wave scenario gives rise to the Heisenberg uncertainty principle according to which position and momentum of an electron can never be measured simultaneously. There’s always an uncertainty.

The wave nature of electrons was experimentally verified by Davisson and Germer experiment, which presented an agreement between the theoretical and the experimental value obtained by de Broglie.

Dual Nature of Radiation and matter concept was widely accepted, and the behaviour of light and matter was now explained based on particle or wave nature which led to more development to modern quantum mechanics—fields like electron optics where development of electron microscopes utilized the concept of wave property of matter.

For exploring intricate concepts of physics to understand and comprehend the topics visit the app or website of MSVGo for interactive videos. The MSVgo philosophy is to enable a core understanding of any concept. These videos coupled with the succinct notes summarizes and showcases all the necessary information.

High School Physics

  • Alternating Current
  • Atoms
  • Communication Systems
  • Current Electricity
  • Dual nature of Radiation and Matter
  • Electric Charges and Fields
  • Electricity
  • Electromagnetic Induction
  • Electromagnetic Waves
  • Electron Beams and Radioactivity
  • Electrons and Photons
  • Electrostatic Potential and Capacitance
  • Fluid Pressure
  • Force and Acceleration
  • Force And Laws Of Motion
  • Gravitation
  • Internal Energy
  • Kinetic Theory
  • Law of motion
  • Light – Reflection And Refraction
  • Magnetic Effects Of Electric Current
  • Magnetism and Matter
  • Management Of Natural Resources
  • Mechanical properties of Fluids
  • Mechanical properties of Solids
  • Motion
  • Motion in a plane
  • Motion in a straight line
  • Moving Charges and Magnetism
  • Nuclear Energy
  • Nuclei
  • Oscillations
  • Our Environment
  • Paths of Heat
  • Physical world
  • Ray optics and optical instruments
  • Semiconductor Devices
  • Semiconductor Electronics: Materials, Devices and Simple Circuits
  • Simple Machines
  • Sound
  • Sources Of Energy
  • Specific and Latent Heats
  • Spherical Mirrors
  • Static Electricity
  • Systems of Particles and Rotational motion
  • Thermal properties of matter
  • Thermodynamics
  • Units and Measurement
  • Vectors, Scalar Quantities and Elementary Calculus
  • Wave Optics
  • Waves
  • Work, Power and Energy

High School Chemistry

  • Acids, Bases and Salts
  • Alcohols, Phenols and Ethers
  • Aldehydes, Ketones and Carboxylic Acids
  • Aliphatic and Aromatic Hydrocarbons
  • Alkyl and Aryl Halides
  • Amines
  • Analytical Chemistry 
  • Atomic Structure
  • Atoms And Molecules
  • Basic concepts of Chemistry
  • Biomolecules
  • Carbon And Its Compounds
  • Carboxylic acids and Acid Derivatives
  • Chemical Bonding and Molecular Structures
  • Chemical Energetics
  • Chemical Equilibria
  • Chemical Kinetics
  • Chemical Reactions And Equations
  • Chemical Reactions and Their Mechanisms
  • Chemistry in Everyday Life
  • Chemistry of p-Block elements
  • Chemistry of Transition and Inner Transition
  • Classification of Elements
  • Coordination Compounds
  • Cyanide, Isocyanide, Nitro compounds and Amines
  • Electrochemistry
  • Electrolysis
  • Elements, Compounds and Mixtures
  • Environmental Chemistry
  • Equilibrium
  • Ethers and Carbonyl compounds
  • Haloalkanes and Haloarenes
  • Hydrocarbons
  • Hydrogen
  • Ideal solutions
  • Introduction to Organic Chemistry
  • Ionic equilibria
  • Matter
  • Matter Around Us
  • Matter In Our Surroundings
  • Metallurgy
  • Metals And Non-Metals
  • Mole Concept and Stoichiometry
  • Natural Resources
  • Organic Chemistry – Basic Principles
  • Periodic Classification of Elements
  • Physical and Chemical Changes
  • Physical and Chemical Properties of Water
  • Polymers
  • Preparation, Properties and Uses of Compounds
  • Principles and Processes of Isolation of Elements
  • Redox Reactions
  • Relative Molecular Mass and Mole
  • States of Matter
  • Structure Of The Atom
  • Study of Compounds
  • Study of Gas Laws
  • Study of Representative Elements
  • Surface Chemistry
  • The d-block and f-block elements
  • The Gaseous State
  • The p-Block Elements
  • The Periodic Table
  • The s-Block Elements
  • The Solid State
  • Thermodynamics

High School Biology

  • Absorption and Movement of Water in Plants
  • Adolescent Issues
  • Anatomy of Flowering Plants
  • Animal Kingdom
  • Bacteria and Fungi-Friends and Foe
  • Biodiversity and Conservation
  • Biofertilizers
  • Biological Classification
  • Biomedical Engineering
  • Biomolecules
  • Biotechnology and its Applications
  • Biotic Community
  • Body Fluids and Circulation
  • Breathing and Exchange of Gases
  • Cell – Unit of Life
  • Cell Cycle and Cell Division
  • Cell Division and Structure of Chromosomes
  • Cell Reproduction
  • Cellular Respiration
  • Chemical Coordination and Integration
  • Circulation
  • Control And Coordination
  • Crop Improvement
  • Digestion and Absorption
  • Diversity In Living Organisms
  • Ecosystem
  • Environmental Issues
  • Excretory Products and their Elimination
  • Flowering Plants
  • Genes and Chromosomes
  • Health and Diseases
  • Health and Its Significance
  • Heredity And Evolution
  • Heredity and Variation
  • How Do Organisms Reproduce?
  • Human Diseases
  • Human Eye And Colourful World
  • Human Health and Disease
  • Human Population
  • Human Reproduction
  • Hygiene
  • Improvement In Food Resources
  • Integumentary System- Skin
  • Kingdom Fungi
  • Kingdom Monera
  • Kingdom Protista
  • Life Processes
  • Locomotion and Movement
  • Microbes in Human Welfare
  • Mineral Nutrition
  • Molecular Basis of Inheritance
  • Morphology of Flowering Plants
  • Neural Control And Coordination
  • Nutrition in Human Beings
  • Organism and Population
  • Photosynthesis
  • Photosynthesis in Higher Plants
  • Plant Growth and Development
  • Plant Kingdom
  • Pollination and Fertilization
  • Pollution; Sources and its effects
  • Principles of Inheritance and Variation
  • Reproduction and Development in Angiosperms
  • Reproduction in Organisms
  • Reproductive Health
  • Respiration in Human Beings
  • Respiration in Plants
  • Respiratory System
  • Sexual Reproduction in Flowering Plants
  • Strategies for Enhancement in Food Production
  • Structural Organisation in Animals
  • Structural Organisation of the Cell
  • The Endocrine System
  • The Fundamental Unit Of Life
  • The Living World
  • The Nervous System and Sense Organs
  • Tissues
  • Transpiration
  • Transport in Plants

High School Math

  • Algebra – Arithmatic Progressions
  • Algebra – Complex Numbers and Quadratic Equations
  • Algebra – Linear Inequalities
  • Algebra – Pair of Linear Equations in Two Variables
  • Algebra – Polynomials
  • Algebra – Principle of Mathematical Induction
  • Algebra – Quadratic Equations
  • Binomial Theorem
  • Calculus – Applications of Derivatives
  • Calculus – Applications of the Integrals
  • Calculus – Continuity and Differentiability
  • Calculus – Differential Equations
  • Calculus – Integrals
  • Geometry – Area
  • Geometry – Circles
  • Geometry – Conic Sections
  • Geometry – Constructions
  • Geometry – Introduction to Euclid’s Geometry
  • Geometry – Three-dimensional Geometry
  • Geometry – Lines and Angles
  • Geometry – Quadrilaterals
  • Geometry – Straight Lines
  • Geometry – Triangles
  • Linear Programming
  • Matrices and Determinants
  • Mensuration – Areas
  • Mensuration – Surface Areas and Volumes
  • Number Systems
  • Number Systems – Real Numbers
  • Permutations and Combinations
  • Probability
  • Sequence and Series
  • Sets and Functions
  • Statistics 
  • Trignometry – Height and Distance
  • Trignometry – Identities
  • Trignometry – Introduction

Middle School Science

  • Acids, Bases And Salts
  • Air and Its Constituents
  • Basic Biology
  • Body Movements
  • Carbon and Its Compounds
  • Cell – Structure And Functions
  • Changes Around Us
  • Chemical Effects Of Electric Current
  • Chemistry in Your Life
  • Coal And Petroleum
  • Combustion And Flame
  • Components Of Food
  • Conservation Of Plants And Animals
  • Crop Production And Management
  • Electric Current And Its Effects
  • Electricity And Circuits
  • Elements and Compounds
  • Fibre To Fabric
  • Food production and management
  • Force And Pressure
  • Forests: Our Lifeline
  • Friction
  • Fun With Magnets
  • Garbage In, Garbage Out
  • Getting To Know Plants
  • Health and Hygiene
  • Heat
  • Hydrogen
  • Life Processes: Nutrition in Animals and Plants
  • Light, Shadows And Reflections
  • Materials: Metals And Non-Metals
  • Matter and Its States
  • Metals and Non-metals
  • Micro Organisms: Friend And Foe
  • Motion And Measurement Of Distances
  • Motion And Time
  • Nutrition In Animals
  • Nutrition In Plants
  • Organization in Living Things
  • Our Environment
  • Physical And Chemical Changes
  • Pollution and conservation
  • Pollution Of Air And Water
  • Reaching The Age Of Adolescence
  • Reproduction In Animals
  • Reproduction In Plants
  • Respiration In Organisms
  • Rocks and Minerals
  • Separation Of Substances
  • Simple Machines
  • Soil
  • Some Natural Phenomena
  • Sorting Materials Into Groups
  • Sound
  • Stars And The Solar System
  • Structure of Atom
  • Synthetic Fibers And Plastics
  • The Living Organisms And Their Surroundings
  • Transfer of Heat
  • Transformation of Substances
  • Transportation In Animals And Plants
  • Universe
  • Waste-water Story
  • Water: A Precious Resource
  • Weather, Climate And Adaptations Of Animals To Climate
  • Winds, Storms And Cyclones

Middle School Math

  • Addition
  • Area and Its Boundary
  • Boxes and Sketches
  • Data Handling
  • Fun With Numbers
  • Heavy and Light
  • How Many
  • Long And Short
  • Mapping
  • Measurement
  • Money
  • Multiplication and Factors
  • Multiply and Divide
  • Numbers
  • Parts and Wholes
  • Pattern Recognition
  • Patterns
  • Play With Patterns
  • Rupees And Paise
  • Shapes And Angles
  • Shapes And Designs
  • Shapes and Space
  • Similarity
  • Smart Charts
  • Squares
  • Subtraction
  • Tables And Shares
  • Tenths and Hundredths
  • Time
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