wave propagation Flashcards

1
Q

(near field) propagation

A

fresnel

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2
Q

(far field) propagation

A

fraunhofer

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3
Q

First order approximation to propagation problem:

A

Geometric Optics

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4
Q

the phase velocity changes in matter
compared to vacuum by a factor

A

n: refraction index

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5
Q

for visible light: n1 ?? 1
for X-rays: n1 ?? 1

A

for visible light: n1 > 1
for X-rays: n1 < 1

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6
Q

n is complex and for X-rays often written as

A

n = 1- delta + i*beta

delta: phase shift of wave in matter
beta: attenuation

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7
Q

The direction of the waves is given
by the

A

wavevector: kn

kn = 2pi / (lambda n)

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8
Q

snells law

A

n0 * sin(theta0) = n1 * sin(theta1)

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9
Q

Huygens-Fresnel principle

A

Optical field in observation plane can be expressed as sum of spherical waves

exp(ikr)/abs(r)

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10
Q

Corpuscular Theory

A

particle theory of light

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11
Q

Interference of light
Double Slit Experiment done by

A

1804 Thomas Young

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12
Q

1804 Intensity of interference
1815 Polarisation done by

A

Augustin Jean Fresnel

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13
Q

Collimated work on electricity and magnetism
of Michael Faraday and André-Marie Ampère done by

A

1864 james clark maxwell

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14
Q

For isotropic media the polarization does not ………and we restrict ourself to …….. waves

A

For isotropic media the polarization does not change and we restrict ourself to scalar waves

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15
Q

à for electromagnetic waves of the velocity c

A

c = lambda * v
c = 1/sqrt(mu0*eps0)

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16
Q

Gauss’ theorem

A

connects the flux of the vector field
through a closed surface surrounding a volume
with the diverence of this field in the volume

divergence of a vector field
within a volume is equal to flux of the vector field
through surface with
normal vector n

17
Q

the integral theorem of Helmholtz and Kirchhoff

A

it allows to calculate the field at point P0 by integrating over a closed surface around P0

18
Q

Geometric optics ………… to describe diffraction and interference

A

insufficient

19
Q

Scalar Theory:

A

only a single component of E or B
and no polarization

20
Q

What are the components of the Fresnel-Kirchhoff diffraction integral

A

Wave Source:

Integration Variables:
two integration variables: one representing the coordinates of the points on the diffracting aperture or obstacle, and the other representing the observation point in the far-field region where the diffracted wave is being analyzed.

Amplitude Factor:

Phase Factor:

Aperture Function:

Geometrical Factor:

21
Q

Paraxial ray is a ray that makes

A

small angle to optical axis

22
Q

With paraxial & Taylor assumptions
* Free space propagation impulse response becomes

A

parabolic shape

23
Q

When to use Fresnel propagation?
Fresnel propagation is valid if

A

Fresnel number F = a*a/(lambda * z) >= 1

24
Q

Fresnel propagation also known as

A

near field

25
Huygens principle assumes
spherical wavefronts
26
Propagated wavefront with Fresnel propagation is given by
by the iFT of the product of Fourier transform of wavefront multiplied by the Fresnel kernel
27
Geometric Optics vs Diffraction
Geometric Optics: straight light rays refraction at surfaces snells law Diffraction: wave propagation diffraction at apertures fresnel-kirchoff integral
28
How do we propagate a wave to the Fresnel regime?
By convolving with a Fresnel propagator (multiplying in Fourier space)
29
Which wavefront shape is assumed by Fresnel diffraction?
parabolic
30
If you propagate the TUM logo with a Fresnel propagator, what would you expect to see?
Slighly higher intensity at the edges of the TUM Logo.