1.
Investigate the nature of light and vision; and describe the role of
invention, explanation and inquiry in developing our current knowledge
a)
b)
c)
identify challenges in explaining the nature of light and vision
investigate the development of microscopes, telescopes and other optical devices;
and describe how these developments contributed to the study of light and other
areas of science
investigate light beams and optical devices, and identify phenomena that provide
evidence of the nature of light

In history, people were known to use light to
their advantage, but they never really knew
what light was.

Pythagoras –
mathematician thought
that light consisted of beams
that came from people’s
eyes in straight lines. Sight
occurred when beams of
touch the objects a person
was looking at.
 Problem: if this is true, we
would be able to see at
night!
 Still accepted for many
years.

Euclid
 Angle of light hitting a flat
mirror is the same as the
angle of light reflected off
the mirror.
 Suggested light travels in
straight lines.

Ptolemy
 Light beams bend when
they go from air to glass.

Al-Haytham – wrote a
book on optics
 First to accurately describe
how the vision works.
 Showed that light bounces
off objects and then travels
to the eye. (light doesn’t
come from the eye but
travels to the eye)

Pythagora’s theory was
abandoned.

Newton – interested in
rainbow colors.
 Using a prism, Newton
showed that white light is a
mixture of different colors.
 As light passes through the
prism, it split into separate
colors.

Michelson – placed mirrors
between two mountains and
measured the distance and
the time it took to send of
beam of light from one
mirror to the other.
 Found the speed of light to be
299 798 kilometers/second.




Light travels in straight lines.
Light can be reflected.
Light can bend.
Light is a form of energy.

Optical devices – any technology that uses
light.
 Example: mirror, Hubble space telescope, glasses

Invention of optical devices has improved
daily.

Hans and Zacharias Jansen – built first
microscope in 1595 (simple design)

Leeuwenhok – used a microscope to look a
pond water, blood and plaque scrapped from
teeth. Found “little animalcules” (actually bacteria,
protozoa, algae, and red blood cells)
 Discovery of microscope lead to new science of
microbiology (study of micro-organisms)

Microscope sees two lenses (one in eyepiece and
one in objectives) and the light to see images in
greater detail.

First telescope made
in 17th century in
the Netherlands
 Telescopes both
magnify and collect
light
 Telescopes provide
enlarged images of
distant objects using
lenses and mirrors.


Built himself a
telescope in one day
and then started to
improve his design
Discovered mountains
and craters on the
Moon, small objects
circling Jupiter, and
then Venus has phases
like the Moon.

Refracting
telescopes – two
lenses (one at each
end of a long tube).
Larger lens collects
light and focuses rays
towards eyepiece.
Eyepiece allows you to
see object larger than
it appears without
telescope

Reflecting
telescopes – uses a
large circular mirror
that curves inward.
Curved surface gathers
light well and another
mirror inside the
telescope directs light
to eyepiece that leads
to the eye.


Too short refracting telescopes fixed together
are called binoculars.
Not as powerful as telescopes but more
convenient.
1.
Investigate the transmission of light, and describe its behaviour using a
geometric ray model
a) investigate how light is reflected, transmitted and absorbed by
different materials; and describe differences in the optical properties
of various materials
b) measure and predict angles of reflection
c) investigate, measure and describe the refraction of light through
different materials
d) investigate materials used in optical technologies; and predict the
effects of changes in their design, alignment or composition

Light travels in straight lines.

Ray diagrams used to show
how light travels.
 Light traveling from source is
shown as straight lines of the
arrows.
 Arrows indicate the direction of
travel.
 Ray diagrams don’t show all light
rays, but are useful in explaining
how light behaves in different
situations.

Example – diagrams can explain brightness
(intensity) changes the distance. Fewer light
rays hit your eyes as you move further away.

Ray diagrams explain shadows:
 Light hits object so light rays cannot continue and a
shadow was formed.

Light acts differently with
different types of materials.
 Transparent materials – transmit
light (light can pass through them)
▪ Example – glass, clear plastic
 Translucent materials – allow
some light (not all) to pass through
them
▪ Example – frosted window pane
 Opaque materials – do not allow
any light to pass through them
(absorbs or reflects the light)
▪ Shadow created behind these materials
▪ Example – wood, metal, brick


Non-luminous materials –
don’t produce light. Light that
gets to the eyes from the
opaque object is reflected from
a light source.
Luminous materials –
produces light itself. Helps us
to see all non-luminous
materials around us.
Type of
material
What happens when Examples Ray diagram
light strikes
Transparent All light is allowed to Clear
pass streaked
glass,
through, transmitted. clear
plastic
Translucent Some light is allowed Frosted
to pass through, some glass,
scattered.
tissue
paper,
wax paper
Opaque
No light passes
through, reflected or
absorbed.
Wood,
desk,
eraser
REGULAR REFLECTION



Light hits a smooth surface
(incoming rays travel parallel to
one another)
All rays are reflected at the same
angle (look the same as though
you hadn’t seen them as a
reflection)
Produced clear image, but eyes
must be in direct path of reflected
rays to see image.
DIFFUSE REFLECTION
 Light hits a rough/uneven
surface
 Each ray is reflected at a
different angle
 Reflected rays don’t remain
parallel.
 When light is scattered, you
see the surface from any
position.

Incident rays – incoming rays
o Smooth surfaces allow incident rays to bounce off
surface in parallel beams. (regular reflection)
o Example – water, mirrors, glass, polished metal

Plain mirrors – flat mirrors with the clearest
reflections
 When a ray of light hits a plane near at an angle, it
bounces off the mirror surface at exactly the same
angle.
Normal – line and perpendicular to mirror
Angle of incidence – angle between the incidents
ray and the normal.
 Angle of reflection – angle between the reflected
ray and the normal.
 Angle of reflection = Angle of incidences


Concave Mirrors
 Surface curves inward (like a bowl, cave)
 Obey the law of reflection
 When the parallel rays hit a curved surface, each
ray is reflected in a different direction.
 Rays all head to the focal point (common point)
 Good at collecting light and bringing it to a single
point.
 Used in flashlights, headlights, cosmetic mirrors,
telescopes to direct as much light possible in a
useful way.


When the object is outside of the focal point,
the image appears upside down. The closer
the image is to the focal point, the larger the
image is.
When object is between the focal point and
the mirror, the image appears enlarged and
right side up.




Mirror with surface curved outwards
Opposite of concave mirror
Spreads out light rays
Image seems to originate from a smaller point
behind the mirror

Light bends when it leaves water, making
objects seem in places that they are not
 Interface – boundary where two different
substances meet

Refraction – light bends when it travels at an
angle from one medium (substance) to another.
o Due to changes in speed of light
o Example - Light in a vacuum = 300 000 km/s (nothing
slows light down)

 When light strikes a medium of different density at an angle,
it will refract.
If a new medium is very dense, the light will slow
down (more refraction)
 Example - Diamonds are more dense than water – high

refraction
When the light slows down, the light bends
towards the normal line.


Lenses collect and bend light
Lens – piece of curved glass (or transparent
material) that refracts light in a predictable
way

Concave lenses

Convex Lenses
 Thinner in the center then at
 Thicker in middle than at
the edges
 Light refracted away from
the center of the lens (light
diverges or spreads out)




edges
Light refracted towards the
center of the lens (light
rays move toward each
other)
Can be used as a light
collector
Forms a real image (light
rays meet at a point and
can be projected on the
screen)
Image is upside down


If the object is behind the focal point, it
appears smaller and upside down.
If the object is between the focal point and
the lens, it appears right side up and
magnified.
1.
Investigate and explain the science of image formation and vision, and interpret related
technologies
a)
demonstrate the formation of real images, using a double convex lens, and predict
the effects of changes in the lens position on the size and location of images
b)
demonstrate and explain the use of microscopes; and describe, in general terms, the
function of eyeglasses, binoculars and telescopes
c)
explain how objects are seen by the eye, and compare eyes with cameras
d)
compare the function and design of the mammalian eye with that of other
vertebrates and invertebrates
e)
investigate and describe the development of new technologies to enhance human
vision
f)
investigate and interpret emerging technologies for storing and transmitting images
in digital form

Eyes and cameras are image of producing
technologies.
Eye
Pupil – allows light into eye
Camera
Aperture – allows light into camera
Iris – colored part of the eyes.
Diaphragm – changes the size of
Controls the size of the pupils and the aperture to allow the proper
the amount of light entering the eye. amount of light in for a picture.
Eyelid – open and closes to let a
certain amount of light in
Shutter – open and close to let
certain amount of light in. The
longer it is open, the more light
enters the camera.

In order to see, light rays strike the retina at the
back of the eye. The retina contains
photoreceptors (cells sensitive to light)
o Two different types of photoreceptors:
 Rods – sensitive to light (can function in low light)
 Cones – detect color (cannot function in low light)


When light hits the retina, photoreceptors are
stimulated and send a message through the optic
nerve to the brain.
Their brain makes sense of the message and
translates it into an image.

Both eyes and cameras have transparent
convex lenses that collect light and direct it to
a focal point
 Lens must be the right shape to produce a good
image
 Muscles of the eye are used to shape the lens to
focus in on an object at different distances.
 Image formed is upside down but the brain
corrects this.



Farsightedness – cannot see close all objects
clearly (image falls behind the retina)
o Convex lens is prescribed
o To converge light
Nearsightedness - cannot see far all objects
clearly (image of falls in front of the retina)
o Concave lenses are prescribed
o To diverge light
Laser eye surgery can be used to fix vision
defects. Surgeon uses a laser to reshape the cornea
of eye. The new cornea acts as a corrective lens.
http://www.learnalberta.ca/content/tlfrbl/index.
html?launch=true


The eye is considered a NATURAL
technology.
The camera is considered an ARTIFICAL
technology.

Camera eyes – eyes that have a cornea,
lens, and retina and are round in shape
o Most vertebrates (animals with backbones)
have the camera eyes.
o Fish have camera eyes with a perfectly
round lens, which bulges out from the
pupil, allowing it to see in practically every
direction.
o Birds have sharper vision than humans
because they have five types of cones
(humans have only 3), each sensitive to
different wavelengths of light.


Nocturnal animals have eyes that collect as
much light as possible because of their very
large pupils.
They also have a layer, called tapetum
lucidum, inside their eye, which acts as a
mirror. They also have many more rods than
cones in their retina making their eyes more
sensitive to low levels of light.

Compound eyes –eyes that
are made of smaller units
called ommatidium.
o Most insects and crustaceans
have compound eyes
o The compound eye is great for
spotting movement, due to
their convex shape, but
with so many lenses, it is
difficult to form a single
coherent image. Instead it
forms a mosaic image (much
like a TV screen).

Most information today is stored digitally
(converted into numbers).

A digital image is a picture made up of smaller
colored pieces called pixels (picture elements).
 Each small pixel is assigned a place and is
represented by a number. This long series of
numbers can then be stored in the memory of a
computer to be accessed at a later time.


Once the individual pixels are in the correct
order, each pixel is assigned a value, which
corresponds to a specific color.
When the picture gets reassembled, the
computer reads the value of each pixel and
makes that pixel the correct color.

The quality of the digital image depends on the
size of the pixels.
o If the pixel is large you will see the image as a
collection of small squares.
o If the pixel is small you will not notice the squares.

The quality of the image is represented by its
resolution. The more pixels there are in the
image, the higher the resolution.


Scanners, digital video recorders, and digital
cameras use a charge-coupled device (CCD)
to capture the light. The CCD is a grid similar
to graph paper.
As the light enters each grid square it creates a
small electrical charge, which is then converted
into digital information and stored on a hard
drive, compact disk or digital tape.


Digital images can be sent over vast distances,
without having to be processed. A powerful
computer can convert the digital information
very quickly.
Digital imaging can also collect different parts
of the electromagnetic spectrum, allowing
infrared as well as visible images to be
captured.