- When light strikes the boundary between two transparent media, it undergoes partial reflection and partial refraction.
- A ray passing from a rarer to a denser medium bends towards the normal, while one passing from a denser to a rarer medium bends away from the normal.
- The angles of incidence and refraction are generally unequal, causing light to bend.
- A ray incident normally (i = 0°) passes undeviated, even though its speed changes.
- Refraction occurs due to a change in the speed of light when it passes from one medium to another.
Topics
Electric Charges and Fields
- Electric Charge
- Conductors and Insulators
- Basic Properties of Electric Charge
- Coulomb’s Law
- Forces between Multiple Charges
- Electric Field
- Electric Field Due to a System of Charges
- Physical Significance of Electric Field
- Electric Field Lines
- Electric Flux
- Electric Dipole
- Dipole in a Uniform External Field
- Continuous Charge Distribution
- Gauss’s Law
- Application of Gauss' Law
Electrostatics
Electrostatic Potential and Capacitance
- Electric Potential and Potential Energy
- Electrostatic Potential
- Potential Due to a Point Charge
- Potential Due to an Electric Dipole
- Potential due to a System of Charges
- Equipotential Surfaces
- Relation Between Electric Field and Electrostatic Potential
- Potential Energy of a System of Charges
- Potential Energy of a Single Charge
- Potential Energy of a System of Two Charges in an External Field
- Potential Energy of a Dipole in an External Field
- Electrostatics of Conductors
- Dielectrics and Polarisation
- Capacitors and Capacitance
- The Parallel Plate Capacitor
- Effect of Dielectric on Capacitance
- Combination of Capacitors
- Energy Stored in a Charged Capacitor
- Overview: Electric Potential
- Overview: Capacitors and Dielectrics
Current Electricity
Current Electricity
- Electric Current
- Electric Currents in Conductors
- Ohm's Law
- Mobility of Electrons
- Drift of Electrons and the Origin of Resistivity
- Limitations of Ohm’s Law
- Resistivity of Various Materials
- Temperature Dependence of Resistivity
- Electrical Energy and Power in Conductors
- Cells, EMF, and Internal Resistance
- Cells in Series and in Parallel
- Kirchhoff’s Laws
- Wheatstone Bridge
- Overview: Electric Resistance and Ohm's Law
- Overview: DC Circuits and Measurements
Magnetic Effects of Current and Magnetism
Moving Charges and Magnetism
- Introduction to Electromagnetism
- Motion in a Magnetic Field
- Biot-Savart Law
- Applications of Biot-Savart's Law > Magnetic Field on the Axis of a Circular Current-Carrying Loop
- Ampere’s Circuital Law
- Solenoid
- Torque on a Rectangular Current Loop in a Uniform Magnetic Field
- Force Between Two Parallel Currents (Ampere’s Law)
- Circular Current Loop as a Magnetic Dipole
- Overview: Moving Charges and Magnetic Field
- Moving Coil Galvanometer
- Overview: Torque on a Current-Loop : Moving-Coil Galvanometer
Electromagnetic Induction and Alternating Currents
Magnetism and Matter
- Concept of Magnetism
- The Bar Magnet
- Magnetic Field Lines
- Bar Magnet as an Equivalent Solenoid
- The Dipole in a Uniform Magnetic Field
- The Electrostatic Analog
- Magnetism and Gauss’s Law
- Magnetisation and Magnetic Intensity
- Magnetic Properties of Materials
- Overview: Magnetism and Mater
Electromagnetic Waves
Optics
Electromagnetic Induction
Dual Nature of Radiation and Matter
Alternating Current
- AC Voltage Applied to a Resistor
- Representation of AC Current and Voltage by Rotating Vectors - Phasors
- AC Voltage Applied to an Inductor
- AC Voltage Applied to a Capacitor
- AC Voltage Applied to a Series LCR Circuit
- Phasor-diagram Solution
- Resonance
- Power in AC Circuit
- Transformers
- Overview: AC Circuits
Atoms and Nuclei
Electromagnetic Waves
- Concept of Electromagnetic Waves
- Displacement Current
- Sources of Electromagnetic Waves
- Nature of Electromagnetic Waves
- Electromagnetic Spectrum
- Overview of Electromagnetic Waves
Ray Optics and Optical Instruments
- Ray Optics Or Geometrical Optics
- Reflection of Light by Spherical Mirrors
- Sign Convention for Reflection by Spherical Mirrors
- Focal Length of Spherical Mirrors
- Mirror Equation of Spherical Mirrors
- Refraction of Light
- Total Internal Reflection
- Applications of Total Internal Reflection
- Refraction at a Spherical Surfaces
- Refraction by a Lens
- Power of a Lens
- Combined Focal Length of Two Thin Lenses in Contact
- Refraction of Light Through a Prism
- Optical Instruments
- Microscope and it’s types
- Telescope
- Overview of Ray Optics and Optical Instruments
Electronic Devices
Communication Systems
Wave Optics
- Concept of Wave Optics
- Huygens' Principle
- Refraction of a Plane Wave
- Refraction at a Rarer Medium
- Reflection of a Plane Wave by a Plane Surface
- Coherent and Incoherent Addition of Waves
- Interference of Light Waves and Young’s Experiment
- Diffraction of Light
- The Single Slit
- Seeing the Single Slit Diffraction Pattern
- Polarisation of Light
- Overview: Wave Optics
Dual Nature of Radiation and Matter
- Dual Nature of Radiation
- Electron Emission
- Photoelectric Effect - Hertz’s Observations
- Photoelectric Effect - Hallwachs’ and Lenard’s Observations
- Experimental Study of Photoelectric Effect
- Effects of Intensity and Frequency on Photocurrent
- Photoelectric Effect and Wave Theory of Light
- Einstein’s Photoelectric Equation: Energy Quantum of Radiation
- Particle Nature of Light: The Photon
- Wave Nature of Matter
- Overview: Dual Nature of Radiation and Matter
The Special Theory of Relativity
Atoms
Nuclei
- Atomic Masses and Composition of Nucleus
- Size of the Nucleus
- Mass - Energy
- Nuclear Binding Energy
- Nuclear Force
- Radioactivity
- Forms of Energy > Nuclear Energy
- Nuclear Fission
- Nuclear Fusion
- Controlled Thermonuclear Fusion
- Overview: Nuclei
Semiconductor Electronics - Materials, Devices and Simple Circuits
- Concept of Semiconductor Electronics
- Classification of Metals, Conductors and Semiconductors
- Intrinsic Semiconductor
- Extrinsic Semiconductor
- n-type Semiconductor
- p-type Semiconductor
- Diode or p-n Junction
- Semiconductor Diode
- Application of Junction Diode as a Rectifier
- Overview: Semiconductor Electronics
Communication Systems
- Detection of Amplitude Modulated Wave
- Production of Amplitude Modulated Wave
- Basic Terminology Used in Electronic Communication Systems
- Sinusoidal Waves
- Modulation and Its Necessity
- Amplitude Modulation (AM)
- Need for Modulation and Demodulation
- Satellite Communication
- Propagation of EM Waves
- Bandwidth of Transmission Medium
- Bandwidth of Signals
The Special Theory of Relativity
- The Special Theory of Relativity
- The Principle of Relativity
- Maxwell'S Laws
- Kinematical Consequences
- Dynamics at Large Velocity
- Energy and Momentum
- The Ultimate Speed
- Twin Paradox
Estimated time: 18 minutes
- Definition: Refraction
- Definition: Refracted Light
- Definition: Refraction of Light
- Key Points: Refraction of Light
Maharashtra State Board: Class 10
Introduction
Refraction is the bending of light when it passes from one medium to another due to a change in speed. This happens because different substances have different densities, which affect how light travels through them.
"Refraction is the change in the direction of a wave as it passes from one medium to another due to a change in its speed."
Causes of Refraction:
- Light changes speed when moving between materials of different densities.
- If light enters a denser medium (e.g., air to water), it slows down and bends towards the normal.
- If light enters a less dense medium, it speeds up and bends away from the normal.
- If light enters perpendicularly, it does not bend but still changes speed.
Maharashtra State Board: Class 10
Activity 1
Pencil in Water (Observing Refraction):
- Take a transparent glass and fill it with water.
- Dip a pencil vertically into the water and observe its thickness.
- Tilt the pencil at an angle and observe again.
- In both cases, the portion of the pencil inside the water appears thicker than the portion above.
- When the pencil is tilted, it looks bent or broken at the water's surface.
This effect occurs because light changes direction (refracts) when it moves from water to air. The bending of light makes the pencil appear distorted, demonstrating the refraction of light.
Maharashtra State Board: Class 10
Activity 2
Disappearing and Reappearing Coin
- Place a 5-rupee coin in a metallic vessel.
- Slowly move away until the coin disappears from view.
- Ask a friend to pour water into the vessel while you keep looking in the same direction.
- As the water level rises, the coin becomes visible again.
Light rays coming from the coin bend when passing from water to air, changing their path. This makes the coin, which was earlier invisible, appear again due to the refraction of light.
Maharashtra State Board: Class 10
Activity 3
Refraction of Light Through a Glass Slab:
- Place a glass slab on a paper and draw its outline (PQRS).
- Draw an inclined ray (AN) on side PQ, marking point N where it meets the slab.
- Fix two pins (A and B) along the ray and look from the other side.
- Align two more pins (C and D) with the images of A and B.
- Remove the slab and draw a line through C and D, meeting SR at point M.
- Join M and N to trace the path of the refracted ray.
Refraction of light passing through a glass slab
Observation and Explanation:
1. The incident ray (AN) strikes the glass at point N and bends due to refraction.
2. The first refraction occurs when light moves from air to glass at N, bending toward the normal.
3. The second refraction occurs when light moves from glass to air at M, bending away from the normal.
The angles of refraction are measured as:
- i = angle of incidence (AN to normal at N).
- r = angle of refraction at N.
- i₁ = r, meaning the refraction inside the glass follows the same pattern.
- e = emergent angle, which equals i due to the opposite bending effect.
The emergent ray (MD) is parallel to the incident ray (AN) but is slightly displaced from it due to the shift caused by the refraction process.
This activity shows that light bends when passing between different transparent media, following the laws of refraction. The incident and emergent rays remain parallel but are slightly displaced, demonstrating the refraction through a rectangular glass slab.
CBSE: Class 12
CISCE: Class 10, 12
CISCE: Class 10, 12
Definition: Refraction
The change in the direction of the path of light when it passes from one transparent medium to another transparent medium is called refraction. The refraction of light is essentially a surface phenomenon.
or
When light passes from one transparent medium to another, its speed and direction change. This is called refraction.
CISCE: Class 10, 12
Definition: Refracted Light
Refracted light is the part of light enters into the other medium and travels in a straight path but in a direction different from its initial direction and is called the refracted light.
CBSE: Class 10, 12
Maharashtra State Board: Class 10
CISCE: Class 12
Maharashtra State Board: Class 10
CISCE: Class 12
Definition: Refraction of Light
When travelling obliquely from one medium to another, the direction of propagation of light in the second medium changes. This phenomenon is known as refraction of light.
OR
Light changes its direction when going from one transparent medium to another transparent medium. This is called the refraction of light.
OR
The bending of the light ray from its path in passing from one medium to the other medium is called 'refraction' of light.
OR
When a ray of light impinges on a polished, smooth, shiny surface, the rebounding of light within the same medium is called reflection of light.
CISCE: Class 10, 12
