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Optics > Optics > Flashcards

Optics Flashcards

1
Q

What is light?

A

An electromagnetic wave (wave with both electric and magnetic parts that does not require a medium and travels at the speed of light)

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2
Q

How is heat energy transferred?

A

Conduction or convection (both require a medium)

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3
Q

How is light energy transferred?

A

Through radiation (light travels through a vacuum, does not require a medium)

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4
Q

Thomas Young

A

Demonstrated that light shows wave-like properties under certain conditions

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5
Q

James Clerk Maxwell

A

Predicted that electricity and magnetism couple together and that the resulting electromagnetic wave does not require a medium for transmission

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6
Q

Heinrich Hertz and William Konrad

A

Hertz: Discovered low-energy electromagnetic waves (radio waves)
Konrad: Discovered high-energy electromagnetic waves (X-rays)

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7
Q

Visible light

A

Electromagnetic waves that the human eye can detect

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8
Q

Electromagnetic system

A

Classification of electromagnetic waves by energy

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9
Q

Visible spectrum

A

Sequence of colours that make up white light (ROYGBIV)

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10
Q

How did Isaac Newton separate white light into the visible spectrum?

A

Within a prism, each colour travels slower than the speed of light in a vacuum
Red light is slowed the least (fastest), violet light is slowed the most (slowest)

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11
Q

Luminous vs non-luminous

A

Luminous: Produces its own light (e.g. Sun, light bulb)
Non-luminous: Does not produce its own light and can only be seen by reflecting light (e.g. tree, pencil)

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12
Q

Incandescence

A

Producing light as a result of high temperature

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13
Q

Incandescent light bulb

A

Thin wire filament becomes so hot as electricity passes through that it gives off visible light

All air from the bulb must be replaced with non-reactive gases so the filament cannot combine with oxygen and burst into flame

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14
Q

Why are incandescent light bulbs inefficient?

A

Only 5-10% of the electricity going through the filament is converted into visible light. The rest is converted into infrared light

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15
Q

Electric discharge

A

Process of producing light by passing an electric current through a gas
(e.g. light from a neon sign)

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16
Q

Phosphorescence

A

Absorbs UV light and releases visible light over an extended period of time (not immediately)

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17
Q

Fluorescence

A

Absorbs UV light and immediately releases the energy as visible light

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18
Q

Fluorescent lights

A

Uses both electric discharge and fluorescence (filled with low-pressure mercury vapour and inner surface of tube coated with fluorescent material)
When turned on, the electric current causes the mercury atoms to emit ultraviolet light, which strikes the fluorescent inner surface of the tube → results in production of visible light

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19
Q

Chemiluminescence

A

Production of light as the result of a chemical reaction
No/little heat is produced → often called “cold light”

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20
Q

How do light sticks use chemiluminescence?

A

1 chemical in main body of stick
1 chemical in small vial in middle of stick
Bending the light stick causes the small glass vial to break, allowing the 2 chemicals to mix in the main body of the stick

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21
Q

Bioluminescence

A

When chemiluminescence occurs in living organisms (e.g. fireflies, glow-worms)

Scientists think organisms use bioluminescence to protect themselves from predators / lure prey / attract mates

22
Q

Triboluminescence

A

Production of light from friction → result of scratching/crushing/rubbing certain crystals.

23
Q

Light-emitting diode (LED)

A

Electronic device that allows an electric current to flow in one direction (achieved by semiconductor)

24
Q

Lasers

A

Produces electromagnetic waves of only one wavelength, and they all move in the same direction.

25
Q

Light ray

A

Line on diagram representing the direction and path that light is travelling

26
Q

Incident light

A

Light emitted from a source that strikes an object

27
Q

Transparent

A

When a material allows all/almost all incident light to pass through (objects can be clearly seen through the material)

28
Q

Translucent

A

Allows some incident light to pass through but absorbs/reflects the rest

29
Q

Opaque

A

Does not allow any incident light to pass through, all absorbed/reflected

30
Q

Virtual image

A

Image formed by light coming from an apparent light source (light does not actually arrive at or come from the image location)

Behind the mirror

31
Q

SALT

A

Size of image (same size, smaller, larger)
Attitude (upright or inverted)
Location of image
Type of image (real or virtual)
Real: image formed when light is actually arriving at the image location (in front of mirror)

32
Q

Law of Reflection

A

Angle of incidence = angle of reflection
Incident ray, reflected ray and normal all lie on same plane

33
Q

Specular reflection vs diffuse reflection

A

Specular reflection: Reflection of light off a smooth surface
Diffuse reflection: Reflection of light off an irregular/dull surface

34
Q

Concave mirror vs convex mirror

A

Concave mirror: Curves or “caves” inward (converging)
Convex mirror: Curves or bulges outward (diverging)

35
Q

Ray diagram rules

A

Travels parallel to the principal axis → reflected through F
Passes through C → reflected back into itself
Passes through F → reflected ray parallel to principal axis
Travels to vertex → reflected at same angle

36
Q

Refraction

A

The bending of light when it travels from one medium into another
Light travels at different speeds in different mediums → when light changes speed, it bends

37
Q

Angle of refraction

A

Angle between the refracted ray and the normal

38
Q

When does light bend toward/away from the normal?

A

Toward the normal when the speed of light in the second medium is slower than in the first
Away from the normal when the speed of light in the second medium is faster than in the first

39
Q

Partial refraction and reflection

A

Some light is reflected off & some is refracted by the surface (e.g. two-way mirrors reflect some of the incident sunlight, reducing AC costs)

40
Q

Index of refraction

A

Ratio of speed of light in a vacuum to speed of light in a different medium

41
Q

Formula for index of refraction

A

n = c/v
n = (sin𝜭i) / (sin𝜭R)

42
Q

Snell’s law

A

n1sin𝜭1 = n2sin𝜭2

43
Q

Phenomena related to refraction: Apparent depth

A

The depth that an object appears to be at due to the refraction of light in a transparent medium

e.g. objects under water appear to be nearer to the surface than they actually are

44
Q

The “flattened” sun

A

When Sun is near horizon during sunset → appears to be flattened
Light from bottom of Sun is refracted more than light from top of Sun
Air is more dense near Earth’s surface → greater bending of Sun’s rays
Light rays from bottom of Sun have a greater angle of incidence than rays from top

45
Q

Mirage

A

Virtual image that forms as a result of refraction and total internal reflection in Earth’s atmosphere

46
Q

Shimmering

A

Shimmering image of moon on water’s surface
Air closer to lake’s surface → warmer
As light ray bends downard → speed increases, so the ray bends farther and farther away from the normal
Eventually, total internal reflection occurs in the lowest warm air layer → results in multiple virtual images of Moon on water’s surface

47
Q

Iris

A

The coloured part of the eye that opens and closes to control the amount of light entering the eye

48
Q

Pupil

A

The hole that lets in light

49
Q

Cornea and lens

A

Converging lens, both are transparent

50
Q

Retina

A

“Film” at the back of the eye that light is focused on
The retina converts the light into an electrical signal that travels along the optic nerve to the brain

51
Q
A

Optics (1 decks)

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