Download Early Work – Mar. 26

Early Work – Mar. 26
• List five ways in which you use a
mirror or a lens on a daily basis.
• Ch. 18 Vocab
18
Mirrors and Lenses
Lab
• Converging and Diverging
Lenses
Early Work – Mar. 26
• Being juniors and seniors in high
school, what type of lab
etiquette should you exhibit?
• Turn in vocab to InBox
Finish Lab
• Lab Etiquette
• 20 minutes to finish
18.1
Mirrors
Mirrors
• Pre-historic man saw his image
reflected to him in water
• Ancient Egyptians used polished
metals to see their images
• In 1857, Jean Foucault
developed a method of coating
glass with silver – letting people
see a clean, clear image of
himself.
Plane Mirrors
• A flat, smooth surface that
reflects light through regular
reflection
– Angle of incidence equals angle of
reflection
object
image
Plane Mirrors
dO = di
hO = hi
Erect Image
Virtual Image
Object
Image
Plane Mirror
Concave Mirrors
Concave Mirrors
Concave Mirrors
Concave Mirrors
Convex Mirrors
Convex Mirrors
Early Work – Mar. 30
• List the three rays to follow to
find an image.
Early Work – Apr. 3
• How can you tell if an image is
real or virtual?
• $2…
Concave Mirror Review
• Principal Axis – line perpendicular to
center of mirror
• Focal Point – point where rays
converge or diverge to
• Center of curvature (or radius) = 2F
• Focal length – distance from focal
point to mirror, f  2f = r
Real v. Virtual
• Real image – rays that converge on a
single point and that image can be
displayed on a screen
– Looking for if rays actually converge at
the point
• Virtual image – image formed
without rays converging on point
Real Images
• Concave mirrors can form real
images – when object is past C
– Three rays to follow
• One parallel
• One through focal point
• One to center of mirror
Image Equations
Magnification – ratio of size of image to size or object
Describing a Real Image
• Mathematically –
– If hi is negative, the image is
inverted
– If di is positive, the image is real
Example
• A concave mirror has a radius of
curvature of 20.0 cm. An
object, 2.0 cm high, is placed
30.0 cm from the mirror.
– Where is the image located?
– How high is the image?
Virtual Images
• Concave mirrors can form virtual images – when
object between F and mirror
– Three rays to follow
• One parallel
• One through focal point
• One to center of mirror
Example
• An object, 2.0 cm high, is placed
5.0 cm in front f a concave
mirror with a focal length of 10.0
cm. How large is the image,
and where is it located?
Early Work – Apr. 9
• Draw the image formed by an
object and a convex mirror.
Describe the image (3).
Spherical Aberration
• When we draw rays, have
them reflect off
perpendicular plane rather
than curved mirror
– Equations even follow this
• But real rays reflect off
curved surface so only rays
close to principal axis
reflect through the focus
18.2
Lenses
Lens History
• Eyeglasses – 13th century
• 1610 – Galileo made telescope
– Observed moons of Jupiter
• Since
– Microscopes
– Cameras
– Solar Powered Marshmallow Roasters
• Probably most useful optical device
Types of Lenses
• Lens – transparent material with
index of refraction larger than
that of air
– Faces can be concave, convex, or
plane
– Convex Lens – thicker in middle.
• Converging lens because light rays
converge to one point on other side.
– Concave Lens – thinner in middle.
• Diverging lens because light rays
spread out on other side.
Types of Lenses
Convex Lenses
• Light refracts at both surfaces of
lens
• For simplicity, we will refract it at
center (perpendicular to
principal axis)
– This is called the thin lens model,
which does apply to the lenses we
talk about
Convex Lenses
Early Work – Apr. 11
• Which lens is a converging lens?
• Which lens is a diverging lens?
• Last day for $2 donation to lens
fund.
• Bkwk due Tues. Apr. 17
Conventions Applied to Lenses
(P430)
• f is positive for convex lenses
• f is negative for concave lenses
• do is positive on the object side of the
lens
• di is positive on the other side (image
side) of the lens, where images are
real
• di is negative on the object side of
the lens where images are virtual
Diagrams
Example
• An object is placed 32.0 cm from
a convex lens that has a focal
length of 8.0 cm.
– Where is the image?
– If the object is 3.0 cm high, how
high is the image?
– Is the image inverted or upright?
Virtual Images
• When an object is in front of the
focal point, a virtual, erect,
enlarged image appears
• A magnifying glass!
Example
• A convex lens with a focal length
of 6.0 cm is held 4.0 cm from an
insect that is 0.50 cm long.
– Where is the image located?
– How large does the insect appear
to be?
Concave Lenses
Lens Defects
Spherical Aberration
Early Work – Apr. 13
• How far behind the surface of
a convex mirror, focal length of
-6.0 cm, does a car 10.0 m
from the mirror appear?
Chromatic Lens
Lens Uses
Nearsightedness
Farsightedness
What we see
Microscope Lenses
Telescope Lenses
Ch 18
• P 439: 1 – 3, 5, 7 – 11, 13 – 15,
18 – 21, 25 - 38