GPO - Propagation and Velocity of Light - Topic 1 Flashcards

1
Q

What is geometrical optics?

A

-This help us to understand the basics of light, reflection and refraction and the use of simple optical elements such as mirrors, prisms, lenses

•Also known as ray optics

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2
Q

What is Physical Optics?

A
  • This help us to understand the phenomena of light wave, interference, diffraction, and polarization; the use of thin film coatings on mirrors to enhance or suppress reflection
  • Also known as wave optics
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3
Q

what is the rectilinear propagation of light?

A
  • Rectilinear propagation describes the tendency of electromagnetic waves to travel in a straight line.
  • Light does not deviate when travelling through a homogeneous medium
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4
Q

What is Huygens’ Principle?

A

Christian Huygens, believed that light was made up of waves vibrating up and down perpendicular to the direction of the light travels, and therefore formulated a way of visualising wave propagation.

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5
Q

What is an optical medium?

A

Any space through which light travels

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6
Q

What are isotropic optical media?

A

Any optical media which has the same properties in all directions

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7
Q

What are homogeneous optical media?

A

Most optical media have these same properties throughout their mass

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8
Q

What are wave fronts?

A

When light starts out from a point source in an isotropic homogeneous medium, it spreads out uniformly at the same speed in all directions,

-Forming such imaginary spherical surfaces.

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9
Q

What is wavelength (λ)?

A
  • Is the distance between successive points of similar phase
  • For eg distance between two successive wave crests in the picture or between two successive troughs
  • nm
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10
Q

What is frequency (ν)?

A
  • Is the number of complete waves produced in one second

* Is expressed in cycle per second called hertz (Hz)

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11
Q

What is Amplitutde (A)?

A
  • Is the peak valve of the wave

* Is a measure of height of the wave crest or depth of the wave trough

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12
Q

What is Velocity (v) ?

A
  • It’s the rate at which the wave travels

- ms-1

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13
Q

What is the velocity of light in a vaccum and for all colours of light?

A

3 x 10^8 ms-1

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14
Q

What is the equation for velocity of light?

A

velocity of light = frequency x wavelength

v = ν λ

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15
Q

A group of light rays is called?

A

A pencil of rays

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16
Q

• The central ray in each pencil is called the

A

chief ray

17
Q

• A pencil of rays can be…

A
  • divergent (go outwards)
  • convergent (go inwards)
  • parallel
18
Q

The vergence at a particular point in a pencil of rays is?

A

is the reciprocal
of the distance from the point to the source or focus
A = 1/a

19
Q

how do we distinguish between diverging and converging rays?

A

a sign convention is applied (+/-)

20
Q

When is the numerical value of the distance given a positive sign?

A

If the distance from the point in question to the source or focus is measured in the SAME direction as that in which light rays are directed

21
Q

When is the numerical value of the distance given a negative sign?

A

If the distance from the point in question to the source or focus is measured in the OPPOSITE direction to that in which light rays are directed

22
Q

What is a dioptre ( 1D) ?

A

One dioptre (1 D) is defined as the vergence in a pencil of rays at a point one metre to the source or focus

23
Q

What are the symbols given to the vergences?

A
Diverging = L
Converging= L'
24
Q

What is the distance from A to the object represented by in converging and diverging light rays?

A
diverging= l
converging= l'
25
Q

When is vergence positive?

A

At any point in a converging pencil of rays

26
Q

When is vergence negative?

A

in a diverging pencil