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Questions and Answers
What happens to a plane wave when it obliquely incident on an interface between two materials?
What happens to a plane wave when it obliquely incident on an interface between two materials?
How does the behavior of a wave at an interface depend on its polarization?
How does the behavior of a wave at an interface depend on its polarization?
Which law governs the relationship between the angles of incidence and refraction in wave propagation?
Which law governs the relationship between the angles of incidence and refraction in wave propagation?
What are the two types of oblique incidence based on the orientation of the electric field?
What are the two types of oblique incidence based on the orientation of the electric field?
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At which specific angle does light behave differently at the interface due to total internal reflection?
At which specific angle does light behave differently at the interface due to total internal reflection?
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What does the wave number or propagation vector represent in the wave equation?
What does the wave number or propagation vector represent in the wave equation?
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In the context of wave propagation, what does the symbol 'k' denote?
In the context of wave propagation, what does the symbol 'k' denote?
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Which of the following correctly defines the condition for lossless unbounded media?
Which of the following correctly defines the condition for lossless unbounded media?
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What is true about parallel polarization (||) in wave interactions?
What is true about parallel polarization (||) in wave interactions?
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How can arbitrary polarization be analyzed?
How can arbitrary polarization be analyzed?
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What does the plane of incidence describe?
What does the plane of incidence describe?
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What role do ε, μ, and σ play in wave propagation between two media?
What role do ε, μ, and σ play in wave propagation between two media?
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What relationship does 'β' express in the context of wave behavior?
What relationship does 'β' express in the context of wave behavior?
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What is the expression for the transmitted electric field intensity in terms of the incident electric field intensity using the transmission coefficient?
What is the expression for the transmitted electric field intensity in terms of the incident electric field intensity using the transmission coefficient?
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What value do Γ⊥ and τ⊥ reduce to when the angles θi and θt are both zero?
What value do Γ⊥ and τ⊥ reduce to when the angles θi and θt are both zero?
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How is the transmission coefficient τ⊥ calculated?
How is the transmission coefficient τ⊥ calculated?
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What does the symbol β represent in the context of transmitted electric field equations?
What does the symbol β represent in the context of transmitted electric field equations?
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Which law relates the angles of incidence and transmission in this context?
Which law relates the angles of incidence and transmission in this context?
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If the incident electric field intensity is Eio = 100 V/m, what is the amplitude of the transmitted electric field intensity Eto when τ⊥ is assumed to be 0.5?
If the incident electric field intensity is Eio = 100 V/m, what is the amplitude of the transmitted electric field intensity Eto when τ⊥ is assumed to be 0.5?
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What characterizes the polarization of the electric field in the discussed scenario?
What characterizes the polarization of the electric field in the discussed scenario?
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What is the effect of increasing the relative permittivity (εr) of the plastic on the transmission coefficient τ⊥?
What is the effect of increasing the relative permittivity (εr) of the plastic on the transmission coefficient τ⊥?
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What is the value of $\theta_r$ based on the relation provided?
What is the value of $\theta_r$ based on the relation provided?
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Which of the following represents the relationship between $\eta_1$ and $\eta_2$?
Which of the following represents the relationship between $\eta_1$ and $\eta_2$?
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What is the value of $\tau_{\perp}$ based on the equation derived?
What is the value of $\tau_{\perp}$ based on the equation derived?
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When deriving $\sin \theta_t$, what condition is used?
When deriving $\sin \theta_t$, what condition is used?
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What does $\epsilon_1$ equal according to the equations given?
What does $\epsilon_1$ equal according to the equations given?
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What is represented by the time-averaged Poynting vector $S_t$?
What is represented by the time-averaged Poynting vector $S_t$?
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Which trigonometric values are used in the calculation of the time-averaged power density?
Which trigonometric values are used in the calculation of the time-averaged power density?
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In the expression for the average power density $S_t$, what is the role of $\eta_2$?
In the expression for the average power density $S_t$, what is the role of $\eta_2$?
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What does the vector $E_t$ depend on in the provided equations?
What does the vector $E_t$ depend on in the provided equations?
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If $\sin(\theta_t) = 0.25$, what is the approximate value of $\cos(\theta_t)$ based on the given information?
If $\sin(\theta_t) = 0.25$, what is the approximate value of $\cos(\theta_t)$ based on the given information?
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What equation is used to express $S_t$ in terms of the vectors involved?
What equation is used to express $S_t$ in terms of the vectors involved?
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What does $\tau_{\perp} E_{io}$ signify in the equations?
What does $\tau_{\perp} E_{io}$ signify in the equations?
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What is the final expression for the average power density $S_t$ given the values?
What is the final expression for the average power density $S_t$ given the values?
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What is the correct expression for the unit vector of the incident wave?
What is the correct expression for the unit vector of the incident wave?
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What does the symbol $k_t$ represent?
What does the symbol $k_t$ represent?
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Which direction is the reflected wave propagating in terms of its components?
Which direction is the reflected wave propagating in terms of its components?
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How is the phase constant for the reflected wave defined?
How is the phase constant for the reflected wave defined?
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What is the significance of obtaining the propagation vector $k$ for wave analysis?
What is the significance of obtaining the propagation vector $k$ for wave analysis?
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The wave vector for the incident wave is expressed as a combination of which components?
The wave vector for the incident wave is expressed as a combination of which components?
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What mathematical representation is used for the unit vector of the reflected wave?
What mathematical representation is used for the unit vector of the reflected wave?
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In the context of wave propagation, what does $ heta_t$ represent?
In the context of wave propagation, what does $ heta_t$ represent?
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Flashcards
Oblique Incidence
Oblique Incidence
When a plane wave hits a boundary between two materials at an angle, it behaves similarly to normal incidence. Part of the wave passes through (transmitted) and part of it bounces back (reflected). The way the wave acts at the boundary depends on its polarization.
Snell's Law
Snell's Law
Snell's Law describes the relationship between the angle of incidence, angle of refraction, and the refractive indices of the two materials. It determines how much the wave bends as it passes from one material to another.
Critical Angle
Critical Angle
The critical angle is the angle of incidence at which the refracted wave travels along the boundary between the two materials. Beyond this angle, there is only reflection and no transmission.
Types of Polarization in Oblique Incidence
Types of Polarization in Oblique Incidence
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Brewster Angle
Brewster Angle
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Propagation Vector (k)
Propagation Vector (k)
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Unit Propagation Vector (ak)
Unit Propagation Vector (ak)
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Angle of Incidence (θt)
Angle of Incidence (θt)
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Angle of Reflection (θr)
Angle of Reflection (θr)
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x-Component of Propagation Vector (kx)
x-Component of Propagation Vector (kx)
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z-Component of Propagation Vector (kz)
z-Component of Propagation Vector (kz)
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Wave Number ("beta")
Wave Number ("beta")
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Incident Wave Propagation Vector in z-direction (ktz)
Incident Wave Propagation Vector in z-direction (ktz)
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Propagation Vector (𝐤)
Propagation Vector (𝐤)
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Plane of Incidence
Plane of Incidence
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Parallel Polarization (||)
Parallel Polarization (||)
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Perpendicular Polarization (⊥)
Perpendicular Polarization (⊥)
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Wave Number (k)
Wave Number (k)
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Phase Constant (β)
Phase Constant (β)
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Poynting Vector (S)
Poynting Vector (S)
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Wave Impedance (𝜂)
Wave Impedance (𝜂)
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Angle of Incidence (𝜃𝑖)
Angle of Incidence (𝜃𝑖)
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Angle of Reflection (𝜃𝑟)
Angle of Reflection (𝜃𝑟)
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Angle of Transmission (𝜃𝑡)
Angle of Transmission (𝜃𝑡)
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Time-averaged Poynting Vector (St)
Time-averaged Poynting Vector (St)
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Calculating St
Calculating St
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Power Density
Power Density
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Units of St
Units of St
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Wave Impedance (η)
Wave Impedance (η)
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St Dependence on E and η
St Dependence on E and η
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Parallel Polarization
Parallel Polarization
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Transmission Coefficient (𝜏⊥)
Transmission Coefficient (𝜏⊥)
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Reflection Coefficient (Γ⊥)
Reflection Coefficient (Γ⊥)
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Energy Conservation Equation
Energy Conservation Equation
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Transmission Coefficient and Snell's Law
Transmission Coefficient and Snell's Law
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Time-averaged Power Density
Time-averaged Power Density
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Material Properties and Light Interaction
Material Properties and Light Interaction
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Perpendicular Polarization
Perpendicular Polarization
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Study Notes
Lecture 4: Oblique Incidence I
- The lecture covers oblique incidence of waves, specifically focusing on the behavior of waves at an interface between two different media.
- Waves experience changes similar to those observed during normal incidence.
- A portion of the wave is transmitted, and a portion is reflected.
- In some cases, only transmission or reflection occurs.
- The wave's behavior at the interface depends on its polarization.
Oblique Incidence
- Waves arrive at an angle.
- Snell's Law and Critical Angle are relevant concepts.
- Two types of polarization are considered: Parallel and Perpendicular.
- Brewster angle is also discussed.
Introduction
- A plane wave incident obliquely on an interface between two materials undergoes changes similar to those during normal incidence.
- Part of the wave is transmitted and part is reflected.
- Wave behavior at the interface depends on wave polarization.
Introduction (cont.)
- Uniform plane wave in general form: E(r, t) = E₀ cos(ωt - kr) aₑ
- General phasor form: E(r) = aₑE₀e⁻ʲᵏ⋅ᵣ
- Position vector: r = xax + yay + zaz
- Wave number (propagation vector): k = kxax + kyay + kzaz
- k = ω√μє
- For lossless unbounded media, k =β
- β = βₓax + βᵧay + βz az
Introduction (cont.)
- Plane of incidence: the plane described by the direction of propagation of the incident wave (kᵢ), i.e., the Poynting vector.
- Normal to the surface at the interface.
- Parallel Polarization (||): E is parallel to the plane of incidence.
- Perpendicular Polarization (⊥): E is perpendicular to the plane of incidence.
- Arbitrary polarization can be treated as a combination of the two components (parallel and perpendicular).
Introduction (cont.)
- Medium 1: ε₁, μ₁, σ₁
- Medium 2: ε₂, μ₂, σ₂
- β₁ = ω√ε₁μ₁
- β₂ = ω√ε₂μ₂
- kᵢ = β₁ sin θᵢ ax + β₁ cos θᵢ az
- kᵣ = β₁ sin θᵣ ax – β₁ cos θᵣ az
- kₜ = β₂ sin θₜ ax + β₂ cos θₜ az
Introduction (cont.)
- Incident wave can be viewed as two components.
- One propagating in the +ve x direction with phase constant kᵢₓ
- One propagating in the +ve z direction with phase constant kᵢz
- kᵢ = kᵢₓax + kᵢz az = β₁ sin θᵢ ax + β₁ cos θᵢ az
- Unit vector for the incident wave: αᵢₖ = kᵢ/|kᵢ| = (sin θᵢ ax + cos θᵢ az)/√(sin² θᵢ + cos² θᵢ)
Introduction (cont.)
- Similarly, reflected wave can be viewed as two components.
Introduction (cont.)
- Similarly, transmitted wave can be viewed as two components.
Introduction (cont.)
- Once k is known, E is defined such that aₖ ⋅ E = 0.
Introduction (cont.)
- Oblique Incidence on a Conducting Interface:
- Incidence from a dielectric medium
- Perfect conductor surface
- No transmitted wave
- Total tangential E must be zero at the interface (z = 0).
Perpendicular Polarization
- E is perpendicular to the plane of incidence
- Incident E is in the +ve y direction
- Eᵢ(r) = aᵧEᵢ₀e⁻ʲᵏᵢ⋅ᵣ
- kᵢ = β₁ sin θᵢ ax + β₁ cos θᵢ az
- Incident wave phase: kᵢ ⋅ r = β₁x sin θᵢ + β₁z cos θᵢ
Perpendicular Polarization (cont.)
- Incident H has -ve x and +ve z components
- H₁(x,z) = [aₖᵢ x Eᵢ (x,z)]/η₁ =...
Perpendicular Polarization (cont.)
- Reflection coefficient, Γ = -1
- Reflection angle θᵣ = incident angle θᵢ
- The total electric field E at the interface is zero.
Perpendicular Polarization (cont.)
- Expressions for E and H are provided.
- Time-averaged Poynting vector, S
Parallel Polarization
- E lies in the incidence plane
- Incident E has two components: one in the +ve x direction, and the second in the -ve z direction
- Incident H is perpendicular to the incidence plane (y-direction).
Parallel Polarization (cont.)
- Reflected fields inside medium 1.
- Tangential components of the electric field at the interface (z=0) must be zero.
- Expressions for E and H are provided
Parallel Polarization (cont.)
- Total fields in material 1.
Oblique Incidence on Dielectric Interfaces
- Incident wave produces a reflected wave in the same material.
- Also, wave propagating in material 2.
- Reflection angle, θᵣ, depends on the incident angle, θᵢ (Snell's law of reflection: ).
- A relation between refraction angle, θₜ, and incidence angle, θᵢ, is needed.
Perpendicular Polarization and its related equations
- The electric field, E, is perpendicular to the plane of incidence (y-direction).
- Medium 1 (permittivity ε₁, permeability μ₁): no conductivity (σ₁ = 0).
- Medium 2 (permittivity ε₂, permeability μ₂): no conductivity (σ₂ = 0)
- Specific equations for the fields (E and H) are given in both media
- Relationship between incident and transmitted angles is given
Perpendicular Polarization and its related equations (cont.)
- The tangential components of E and H are equated on both sides of the interface(z=0)
- Equations to determine the reflection and transmission coefficients (Г and τ) are derived.
Example Calculations
- Calculations for time-averaged power density.
- Explicit values for various parameters are provided.
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Description
Test your knowledge on wave propagation when a plane wave encounters an interface between two materials. This quiz covers the effects of polarization, laws of reflection and refraction, and specific behaviors like total internal reflection. Dive into the fundamental principles governing wave interactions and their mathematical representations.