grade 8 science unit 2: optics - lushman's...
TRANSCRIPT
Grade 8 Science
Unit 2: Optics
Chapter 6:
Lenses refract light to form images.
Lenses
A curved piece of
transparent material that
refracts light in a
predictable way.
Usually made from glass or
plastic.
Lense
s
There are two types of lenses:
1. Convex
Centre of the lens bulges out
Causes light rays to bend toward each other (converge)
2. Concave
Centre of the lens is curved
in
Causes light rays to bend
away from each other
(diverge)
Conve
x v
s. C
onca
ve L
ense
s
Convex Lenses
Can act as a magnifying
glass
Corrective Lenses
The Eye (pg. 229)
Vis
ion
Near-sighted Vision
See objects up close but
not at a distance.
Concave lenses are used to
correct this vision.
Near
- si
ghte
d V
isio
n
Far-sighted Vision
See objects at a distance
but not up close.
Convex lenses are used to
correct this vision.
Far
-sig
hte
d V
isio
n
CORE
STSE:
“Fibre
Optics” Fibre Cable
Optical Technologies...
1. Microscopes
Uses two convex lenses
with relatively short focal
points to magnify
Magnified twice to
increase enlargement
The M
icro
scope
2. Telescopes
The objective lens has a
longer focal length than the
microscope.
Can have either a refracting
or reflecting telescope
Refracting Telescope (pg. 245)
The lenses bend light to
focus it.
The objective lens must be
as large as possible to view
distant galaxies (makes it
heavy)
Reflecting Telescope (pg. 246)
Uses a concave mirror, plane mirror and a convex lens to collect and focus light from objects at a great distance.
Most large telescopes are this type.
The Hubble Space Telescope
Launched in 1990
The Reflecting
Telescope
3. Cameras (pg. 248)
4. Binoculars (pg. 247)
5. Face shields
6. Magnifying glasses
7. Contact lenses
8. Flashlights
9. Eye glasses
The Nature of Science
The development of new technologies involve many individuals and groups of people.
These technologies can alter what we know about the nature of science.
1602
1672
Individuals...
Galileo
Newton
Groups...