2.4 - Optics Flashcards

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1
Q

What is meant by Chromatic Aberration

A

Aberration means a departure from the expected or proper course

Dispersion is a serious problem that the makers of optical instruments with lenses have to solve.

Dispersion means that red light is brought to a focus further away from a positive lens than blue light is.

This blurs images, an effect called chromatic aberration.

Newton solved the problem for telescopes by designing one in which the light was focuses by a curved mirror

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2
Q

Converging (Convex) lens

If object outside the focus?

if object inside the focus?

A

Converging (Convex) lens

If the object is outside the focus the image is real and is located at the opposite side of the lens to the object. The image will be inverted (COIRO)

If the object is inside the focus the image is virtual and is located at the same side of the lens to the object. The image is upright

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3
Q
A
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4
Q

A mirror

a) absorbs come of the light
b) refracts some of the light
c) reflects some of the light

A

a) absorbs come of the light

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5
Q

What is meant by Attenuation?

A

The loss of optical power as light travels along the fibre caused by

Absorption

Scattering

Bending losses

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6
Q

In terms of loss of optical power through attenuation.

What causes absorption

A

Atomic imperfections, impurities (water, oxygen defects)

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7
Q

In term absorptions of loss of optical power through attenuation.

What causes Scattering

A

Fibre density changes - light scattered in all directions

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8
Q

In terms of loss of optical power through attenuation.

What causes bending

A

Macrobends - fibre bend radius too small

Microbends - clamping too tight, external forces

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9
Q

What is the speed of light in a vacuum?

A

3 x 108 m/s

Note in a vacuum, this speed decreases in our atmosphere

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10
Q

Concave Mirrors

When real image and when virtual?

A

If an object is outside the focus the image is real

If the object is inside or at the focal point the image is virtual

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11
Q

Fibre optics depends on (is based off) the ______ of light rays

A

total internal reflection

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12
Q

What is the bending or changing of direction of light called

A

refraction of light

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13
Q

When Launching light into the fibre,

The acceptance cone is ________

The acceptance angle is _____________________

A

When Launching light into the fibre,

The acceptance cone is three-dimensional

The acceptance angle is 1/2 angle of the maximum cone of light that can enter or exit the fiber

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14
Q

What is the eqaution relating refractory index and how fast light will travel through a substance?

A

N = C / V

Where

N = index of refraction

C = celerity (speed of light in a vacuum)

V = speed of light in that substance

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15
Q

What is the difference between angle of incidence and angle of refraction?

A

angle of incidence i is the angle at which light strikes the object

angle of refraction is the bending of light when it goes through or hits an object

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16
Q

In order for light to bounce off a medium and not enter it, it must be _______ to the critical angle

A

greater

17
Q

What is the equation for snell’s law and what does it mean

A

n = sin i / sin r

where n = refractive index

i = angle of incidence

r = angle of refraction

The refractive index determines how much the path of light is bent or refracted when entering a material

18
Q

What does the refractive index n mean?

A

The refractive index determines how much the path of light is bent or refracted when entering a material

19
Q

Make a table with concave/convex mirror/lens under image and image location

A
20
Q

To test for a splice of a fibre optic cable, what is used?

A

OTDR

Optical Time Domain Reflectometer

21
Q

What are the 2 types of rays found in Fibre optic cables?

A

Meridional Rays - Rays that pass through the centre axis of the fibre

Skew rays = rays that travel through the fibre without passing through the centre axis