Light & Optics 3-4 Flashcards
(51 cards)
1
Q
what is the wave model of light?
A
- Commonly used by
scientists - Waves and light are
both forms of energy - They both travel out in
all directions
2
Q
what are the (4) properties of waves?
A
- Amplitude: Height of a wave from rest to the crest
- Crest: Highest point of a wave
- Wavelength: Distance from the crest of one wave to the crest of
another - Frequency: number of times the medium vibrates in a given unit of
time
3
Q
what is a wavelength?
A
- All waves have a wavelength
- Wavelengths can vary greatly
- Wavelength relates to frequency
- The more waves you create per
second the higher the frequency - The higher the frequency the
shorter the wavelength
4
Q
what are light waves?
A
- The colours of a rainbow comprise the visible light spectrum
- White light is made of all the different colours of the rainbow
- Each of the colours have a different wavelength
- Red light is on one end (longest wavelength)
- Violet light is on the other end (shortest wavelength)
5
Q
what is the invisible spectrum?
A
- Many wavelengths fall outside of the range that can be seen
by our eyes
6
Q
what is electromagnetic radiation and the electromagnetic spectrum?
A
- Electromagnetic radiation: All forms of radiant energy
- Electromagnetic spectrum: All wavelengths of radiant
energy, visible and invisible
7
Q
what are radio waves?
A
- Longest wavelength
- Vital to communication
around the world - FM radio waves are
longer than AM radio
waves
8
Q
what is MAGNETIC RESONANCE
IMAGING (MRI)?
A
- Radio waves sent into the body
- Energizes the atoms in the body
- When the radio pulse stops
atoms go back to their original
position and release the energy
which then creates a picture on
the computer screen
9
Q
what are microwaves?
A
- Shorter than radio waves
- Higher frequency than radio
waves, therefore they carry more
energy - Used to heat food
- The energy in the wave causes
the water particles in the food to
vibrate, warming it up.
10
Q
what is RADAR?
A
- An acronym for radio detection and
ranging - Early radar devices used radio waves
- Send out short bursts of microwaves
to detect objects - Follow the law of reflection
- Knowing how long it takes for
microwave to be released and return
to the receiver we can calculate
distances
11
Q
what are infrared waves?
A
- Can’t be seen, but can be felt as
heat - Special equipment can sense
infrared radiation - Images of infrared radiation are
called thermograms
12
Q
what is the visible spectrum?
A
the light we see
13
Q
what is ultraviolet (UV)?
A
- Carries more energy than visible
light - Can burn skin and increases the
risk of skin cancer - Most UV rays are absorbed by
the Earth’s ozone layer - Sunblock provides an opaque
layer that prevents UV rays from
reaching your skin
Chemical override, ultraviolet
You could be mine tonight
14
Q
what are the uses of UV light?
A
- Used in hospital, and food processing
plants to kill microorganisms - Small dose of UV necessary for humans,
produces vitamin D - Babies born with jaundice, a liver
condition which causes yellow skin, are
placed under UV lamps to cure the
condition
15
Q
what are x-rays?
A
- Extremely high energy radiation
- Can penetrate tissue
- Lower energy x-rays have trouble
passing through bones, useful for
medical imaging - X-ray technicians protect
themselves and other parts of
your body with lead aprons
– Rays cannot penetrate lead
16
Q
what are gamma rays?
A
- Highest energy radiation on the
spectrum - Can penetrate tissue
- Used to kill cancer cells
- Only used in short bursts, long
term radiation could cause
cancer
17
Q
what are artificial sources of light?
A
- Light sources that are not
naturally occurring - Make our lives much more
convenient - We use them a lot throughout
the day
18
Q
what is incandescent light?
A
- The filament is a thin piece of wire
- Electrical energy flows through the
filament, which heats the filament - The filament gets so hot it begins to
glow - The light you see is the filament
glowing
Your touch brought forth an incandescent glow
19
Q
what is fluorescent light?
A
- Glass tube filled with a small amount of gas Ex.
Mercury vapour - Inside of the tube is coated with phosphor
- Phosphor emits light when exposed to UV
rays - Electricity passes through the tube many times
per second - Every time electricity passes through the gas
emits UV rays - UV rays strike the phosphor and it emits
visible white light
20
Q
what is phosphorescent light?
A
- Some substances have the ability to
store energy when radiation hits them - They can emit light for a long time
after the radiation has stopped - Phosphorescence: ability to emit
light - Example: Glow in the dark items
21
Q
what is energy efficiency?
A
- Many light bulbs are incredibly
inefficient, up to 95% of the energy
they give off is heat and only 5% is
light (Think incandescent bulbs) - Other options like fluorescent and
LED are more efficient and release
less heat.
22
Q
what is bioluminescence?
A
- When living organisms produce
their own light - Fireflies have a photophore, a
light producing organ - Light is created by a chemical
reaction - Deep sea organisms like the
angler fish need to create their
own light because the suns rays
do not reach that deep
23
Q
what are the basics of the colors of light?
A
- We know visible light is comprised of colours, ranges from red to violet
- Each colour has a different wavelength, so they refract slightly different amounts
- If we combine all the colours together we know we will get white light
24
Q
what are the basics of adding colors of light together?
A
- To get white light we really only need
to combine red, green and blue - Primary colours (of light): red, green
and blue. These colours can be
combined to create all other colours - Secondary colour: made by
combining two primary colours.
(magenta, yellow and cyan)
25
how does tv light work?
* A television’s picture is made up
of a series of small dots
* Dots are lit as on of the primary
colours
* Based on the combination of
different colours in an area your
eye is fooled into seeing
secondary colours or white
26
know the structure of an eyeball
- optic nerve
- vitreous gel
- iris
- cornea
- pupil
- lens
- iris
- retina
- macula
27
how does light get into your eye?
* The hole in the human eye is known as the
pupil
* The pupil is created by a circular band of
muscle, the iris (coloured part of your
eye)
* Iris controls the size of the pupil, therefore
how much light gets into the eye
* In dim light the pupil dialates (become
wider)
* In bright light the pupil constricts (gets
smaller)
* Change in pupil size happens automatically
28
how does a camera get light in and take pictures?
* An eye and a camera use the same
method of letting light in through a hole
* Instead of a pupil a camera has an
aperture
* The diaphragm of the camera lens
changes the size of the aperture
* Shutter opens when you press the button,
allowing light in
* Longer the shutter is open, more light
comes in
29
what happens after light gets in your eye?
* To see light must hit the retina on
the back of the eye
* The retina has photoreceptors, cells
that are sensitive to light
* Two types of photoreceptors
– Rods: highly sensitive to light
– Cones: detect colour
* Rods function in low light, cones do
not this is why you see in shades of
grey in low light
30
how do your eyes focus light?
* Good vision requires light hitting the retina properly
* Your eye uses a lens to focus light
* Eye lens in double convex
* There are ciliary muscles around the lens that contract and change
the shape of your lens, focusing the light
31
what happens after light/the image strikes the retina?
* Photorecpetors are stimulated
and send signals to the optic
nerve
* The nerve connects to the brain
* The brain translates the signals
into an image
32
what is the blind spot?
* Small spot on the retina
where there are no
photoreceptors
* Where the optic nerve
attaches to the eye
* Brain gets no info about a
small area of whatever
you’re looking at
33
what happens when the image is formed on the retina?
* The image formed on your retina is upside down
* Your brain corrects for this and flips the image
* You interpret the world right side up
34
what is myopia?
NEARSIGHTEDNESS
* Cannot see distant objects clearly
* The eye cannot make the lens
thin enough to focus light on the
retina
* The image falls in front of the
retina
* Concave lens prescribed
35
what is hyperopia?
FARSIGHTEDNESS
* Cannot see close
objects clearly
* Eye cannot make the
lens fat enough to focus
light on the retina
* Image falls behind the
retina
* Convex lens prescribed
36
what is laser eye surgery?
* Use a laser to reshape the cornea of
the eye
* Cornea: clear outer covering of the
eye
* Doctor cuts the flap of tissue
covering the eye and folds it to the
side
* Reshaped cornea acts as a corrective
lens
37
what are night vision goggles and how do they work?
* Now matter how good your vision
is, you’re not great as seeing in low
light
* Night vision goggles project light
onto an intensifier
* The intensifier releases a stream of
particles
* The particles hit a phosphor coated
screen
* The phosphor glows green, person
sees a glowing green image
38
what are camera eyes?
* The design of a human eye is roughly
the same as a camera
* Eyes that have a cornea, lens and retina
and are roughly a round shape are
referred to as camera eyes
* Most vertebrates have camera eyes
* Depending on the usage of the eye
structure might be slightly different.
39
what are fish eyes?
* Instead of an oval shaped lens
their lens is completely round
* The lens bulges out through the
pupil
* Because the lens sticks out a fish
can see in practically every
direction
40
what are bird eyes?
* Have much sharper vision than
humans
* Humans have 3 types of cones, one
for each of red, green and blue light
* Birds have 5 types! They are
sensitive to different wavelengths
* This means birds can see more
colours and shades
41
what is nocturnal?
* Animals that are awake at night
* No animal can see in complete darkness
* Nocturnal animals have eyes that allow
them to collect as much light as possible
* Very large pupils
* A structure called the tapetum
lucidum acts as a mirror to reflect light
within the eye
* Have more rods than cones
42
what are compound eyes?
* Found in insects and crustaceans
* The eye is made of many smaller
units
* Each individual unit is known as an
ommatidium
* Ommatidium looks like a long tube
with a lens connected to a focusing
tube which leads to a light sensitive
cell
* Insect eyes have convex surface
which allows them to detect motion
in almost any direction
43
what are the drawbacks of compound eyes?
* Difficult to form a single coherent
image
* Made up of lots of small dots of light
* The image is known as a mosaic
image
* The more ommatidia, the clearer the
image
44
what is the brains role in image storage and transmission?
* Big role in sorting, storing and
retrieving info about images you
have seen
* Receives and send signals as
electrical impulses on neurons
* Scientists are still studying why
some images remain stored in our
brain for a long time and others
fade quickly
45
what is (traditional) photography?
* We need a reliable way to
recall images completely and
accurately
* Traditional photography uses
film and chemicals to store
information.
* Over time chemicals react and
change.
* Traditional photographs can
fade
46
what is a stadium image?
* People in a sports stadium forming a
large image.
* Each person gets a card to hold up
* When viewed from across the
stadium and image is formed
* Up close it’s a bunch of individual
coloured cards
* To stay organized each card is given a
specific coordinate (seat
(think eras tour bracelets making rainbows, hearts, ect.)
47
what is a digital image?
* Also creates a big image with
small pieces
* Digital images are split up into
small elements called picture
elements (pixels)
* Each pixel has a coordinate and
a number which are stored by
the computer
* The computer can read the
string of coordinates and
numbers to form the picture
48
how does coloring digital images work?
* In digital imaging the computer
assigns a number to each pixel
* The number corresponds to a
certain colour
* When the computer reads the
information the numbers tells it
what colour the pixel should be
49
what determines digital image quality?
DIGITAL IMAGE QUALITY
* Dependent on pixel size
* Larger the pixel, lower quality
* Poor quality digital images are
known as low resolution
* Low resolution has less pixels per
given area
50
how do we capture digital images?
* Work like a regular camera, light
enters aperture and falls onto a light
sensitive surface
* The surface is a charge-coupled
device (CCD).
* A CCD is a grid
* As light falls on a square it creates a
small amount of electricity
* Charge is converted into digital
information
51
how do we transmit digital images?
* You can send digital information
much further than a hard drive
* We can use EMR to send pictures
great distances.
* Imagine if the images from
satellites were on regular film!
* Using digital imaging we can also
capture “invisible” parts of the
spectrum
