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...