Topics
Electric Charges and Fields
- Electric Charge
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- Properties of Electric Charge
- Coulomb’s Law
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- Continuous Charge Distribution
- Gauss’s Law
- Application of Gauss' Law
Electrostatics
Current Electricity
Electrostatic Potential and Capacitance
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Magnetic Effects of Current and Magnetism
Current Electricity
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Electromagnetic Induction and Alternating Currents
Moving Charges and Magnetism
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- Applications of Biot-Savart's Law > Magnetic Field at the Axis of a Circular Current-carrying Loop
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Magnetism and Matter
Electromagnetic Waves
Electromagnetic Induction
Optics
Dual Nature of Radiation and Matter
Alternating Current
Electromagnetic Waves
- Introduction to Electromagnetic Waves
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Atoms and Nuclei
Electronic Devices
Ray Optics and Optical Instruments
- Ray Optics Or Geometrical Optics
- Reflection of Light by Spherical Mirrors
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- Focal Length of Spherical Mirrors
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- Refraction of Light
- Total Internal Reflection
- Applications of Total Internal Reflection
- Refraction at a Spherical Surfaces
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- Power of a Lens
- Combined Focal Length of Two Thin Lenses in Contact
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- Introduction to Optical Instruments
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Wave Optics
- Introduction to 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
Communication Systems
Dual Nature of Radiation and Matter
- Understanding Dual Nature of Radiation and Matter
- 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
The Special Theory of Relativity
Atoms
Nuclei
Semiconductor Electronics - Materials, Devices and Simple Circuits
Communication Systems
- Detection of Amplitude Modulated Wave
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- Sinusoidal Waves
- Modulation and Its Necessity
- Amplitude Modulation (AM)
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- Satellite Communication
- Propagation of EM Waves
- Bandwidth of Transmission Medium
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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: 7 minutes
CBSE: Class 12
Introduction
When light travels from an optically denser medium to an optically rarer medium, its speed increases in the second medium and the refracted ray bends away from the normal.
For refraction between two media, Snell’s law is: n1sin i = n2sin r
For denser to rarer transition, n1 > n2, so the refracted angle is greater than the angle of incidence.
CBSE: Class 12
Definition: Rarer Medium
A rarer medium is a medium in which light travels faster and whose refractive index is lower compared with the denser medium.
CBSE: Class 12
Definition: Critical Angle
The critical angle is the angle of incidence in the denser medium for which the angle of refraction in the rarer medium becomes 90 degrees.
If i = ic, then the refracted ray travels along the boundary surface.
CBSE: Class 12
Definition: Total Internal Reflection
Total internal reflection is the complete reflection of light back into the denser medium when light travels from a denser to a rarer medium, and the angle of incidence becomes greater than the critical angle.
CBSE: Class 12
Derivation of critical angle
At the critical angle,
- angle of incidence = ic
- angle of refraction = 90°.
Using Snell’s law,
n1sin ic = n2 sin 90∘
Since sin 90∘ = 1,
n1 sin ic = n2
Therefore,
sin ic = \[\frac {n_2}{n_1}\]
CBSE: Class 12
Condition flow
| Condition | Result | Meaning |
|---|---|---|
| (i < ic) | Refraction occurs | Light passes from the denser medium into the rarer medium. |
| (i = ic) | r = 90° | The refracted ray grazes along the surface. |
| (i > ic) | Total Internal Reflection (TIR) | No refracted ray enters the rarer medium; the light is completely reflected back into the denser medium. |
Related QuestionsVIEW ALL [6]
| A ray of light travels from a denser to a rarer medium. After refraction, it bends away from the normal. When we keep increasing the angle of incidence, the angle of refraction also increases till the refracted ray grazes along the interface of two media. The angle of incidence for which it happens is called critical angle. If the angle of incidence is increased further the ray will not emerge and it will be reflected back in the denser medium. This phenomenon is called total internal reflection of light. |
For which of the following media, with respect to air, the value of critical angle is maximum?
| A ray of light travels from a denser to a rarer medium. After refraction, it bends away from the normal. When we keep increasing the angle of incidence, the angle of refraction also increases till the refracted ray grazes along the interface of two media. The angle of incidence for which it happens is called critical angle. If the angle of incidence is increased further the ray will not emerge and it will be reflected back in the denser medium. This phenomenon is called total internal reflection of light. |
A ray of light travels from a medium into the water at an angle of incidence of 18°. The refractive index of the medium is more than that of water and the critical angle for the interface between the two media is 20°. Which one of the following figures best represents the correct path of the ray of light?
