Electromagnetic Radiation

Question 1

Wave - Particle Duality

Answer 1

• when dealing with its propagation, light is best described by waves
• when dealing with energy, light is best described as particles

Question 2

Faraday’s Law

Answer 2

induced EMF = - rate of change of magnetic flux through circuit
∂E/∂x = - ∂B/∂t

Question 3

Electrostatic Force

Answer 3

^F = k q1q2/r (^r12) = q^E

Question 4

Magnetic Force

Answer 4

^F = q^v x ^B

Question 5

Maxwell’s Formulation of Faraday’s Law

Answer 5

dE/dB = dx/dt

Question 6

Maxwell’s Formulation of Ampere’s Law

Answer 6

∂B/∂x = μ0 ε0 ∂E/∂t

Question 7

Perpendicular E and B Fields and the Wave Equation

Answer 7

-for perpendicular E and B fields starting from Maxwell’s formulation of Ampere’s Law and Faraday’s Law respectively it is possible to show that both B and E obey the wave equation

Question 8

Wave Speed

Answer 8

-Maxwell’s equations give a wave speed
v = 1/√(μ0 ε0) = c
-Maxwell had discovered the electromagnetic wave nature of light

Question 9

Electromagnetic Waves

Answer 9

• Maxwell found that electromagnetic waves should exist

- oscillating electric and magnetic fields perpendicular to each other and the direction of propagation

Question 10

Harmonic Travelling Wave Solutions of the Wave Equation

Answer 10

B = B0 cos(kx-t)

E = E0 cos((kx-ωt)

Question 11

Travelling Waves Velocity Equation

Answer 11

v = ω/k

Question 12

Electromagnetic Waves - Field Amplitudes Equation

Answer 12

E0 = cB0
and since the waves are in phase
E = cB

Question 13

The Del Operator, ∇

Answer 13

∇ = ∂/∂x i + ∂/∂y j + ∂/∂z k

Question 14

∇f

Answer 14

gradient of a scalar function is a vector quantity

Question 15

∇.A

Answer 15

divergence of a vector is a scalar quantity

Question 16

∇xA

Answer 16

curl of a vector is a vector quantity

Question 17

∇²A

Answer 17

the Lalacian of a scalar A

Question 18

The Propagation of Light - Huygen’s Principle

Answer 18

• all points on a wavefront are taken as point sources for the production of spherical secondary waves called wavelets
• wavelets propagate outwards at the characteristic speed of waves in that medium
• after some time has elapsed, the new position of the wavefront is the surface tangent to the wavelets

Question 19

Interference

Definition

Answer 19

-the combining by superposition of two or more waves of the same frequency

Question 20

Diffraction

Definition

Answer 20

• the phenomenon whereby an aperture behaves like a source

- it causes waves to travel around corners, when a portion of a wave-front is cut off by a barrier

Question 21

Intensity and Amplitude

Answer 21

I ∝ A²