Transcript Document

A.
B.
C.
D.
23000000 m
2300 m
.0023 m
.0000023 m
[Default]
[MC Any]
[MC All]
• Nanometer (nm) = .000000001 m = 10-9 m
• Angstrom (Å) = .0000000001 m = 10-10 m
• A large number of equally spaced parallel slits is
called a diffraction grating.
• A diffraction grating can be thought of as an
optical component that has tiny grooves cut into it.
The grooves are cut so small that their
measurements approach the wave length of light.
• A diffraction grating
splits a plane wave
into a number of
subsidiary waves which
can be brought
together to form an
interference pattern.
If you now send the light from the two openings onto a screen, an
interference pattern appears, due to differing path lengths from each
source
• we have constructive interference if paths differ by any number of
full wavelengths
• destructive interference if difference is half a wavelength longer or
shorter
Constructive interference
Constructive interference
Destructive interference
Geometry
Path length difference
Constructive interference
Destructive interference
d (sinq) = m l
d = grating spacing
q = angle of deviation
m = order of magnitude
l = wavelength
X
θ
θ
Y
d
θ
Path difference
= d sin θ
• If d is the slit spacing then the
path difference between the
light rays X and Y = d sin θ.
• For principal maxima,
d sin θ = mλ.
• The closer the slits, the more
widely spaced are the
diffracted beams.
• The longer the wavelength of
light used, the more widely
spaced are the diffracted
beams.
• A spectrometer is a device to measure wavelengths
of light accurately using diffraction grating to
separate.
Turntable
Diffraction grating
Collimator C
θ
Light
source
Telescope T
Eyepiece
Achromatic
lenses
Eye
Cross-wire
• Diffraction grating
placed in front of a
methane air flame
 Spectrum of a star
- Procyon
A.
B.
C.
D.
6.328 x 10-7 m
1.58 106 m
1.505 x 105 m
6.64 x 10-6 m
A.
B.
C.
D.
3.2 degrees
5.5 degrees
6.7 degrees
8.5 degrees
A.
B.
C.
D.
13.12 degrees
11.25 degrees
10.98 degrees
9.46 degrees
A.
B.
C.
D.
blue
violet
white
red
A.
B.
C.
D.
The distance decreases
The distance increases
The distance stays the same
The distance goes to zero
Law of Reflection
• Incoming and Reflected angles are equal
• Normal is perpendicular to surface at point of
reflection
Normal
Mirrors
• Planar
• “flat” mirrors
• Spherical
• Concave
• Convex
Some Terminology
• Center of Curvature (C)
• Principle Axis
• Focal Point (F)
F
Ray Diagrams
• Image location can be predicted with ray diagrams
• All you need to do is draw the three Principle Rays to
determine the location, orientation, and size of the image.
Principle Rays
1.
Draw a ray coming from the top of the object, parallel to the axis.
It reflects through the focal point.
Principle Rays
2.
Incident ray is through focal point, reflects parallel to axis.
Principle Rays
3.
Incident ray is through center of curvature, reflects straight back.
Ray Diagram
•
•
See where the 3 rays converge? That’s the location of the image.
For this situation, the image is smaller and inverted.
Ray Diagrams
• Image location can be predicted with ray diagrams
• Image may appear in front of the mirror – real image
• Real images can be seen reflected onto a sheet of paper.
• Image may appear behind the mirror – virtual image
• Virtual images cannot be seen reflected onto a sheet of paper.
Real vs. Virtual Images
• The virtual image in a plane mirror will appear as far
from the mirror as the object, so if you stand 2 m in
front of the mirror, your reflection appears to be 4m
away from you.
Simple Camera
Real image
Virtual image
A penguin looks into a planar (flat) mirror
and sees his image on the other side of
the mirror. What type of image is
formed?
A.
B.
C.
D.
real
fake
virtual
imaginary
Convex Lenses
Thicker in the center than
edges.
• Lens that converges
(brings together) light
rays.
• Forms real images and
virtual images depending
on position of the object
The Magnifier
Concave Lenses
• Lenses that are thicker
at the edges and
thinner in the center.
• Diverges light rays
• All images are
upright and reduced.
The De-Magnifier
Convex Lenses
Rays traveling parallel to the principal
axis of a convex lens will refract
toward the focus.
•2 •F
•F 2F
•
•2 •F
•F 2F
•
F
Rays traveling from the focus will
refract parallel to the principal
axis.
F traveling directly through the
Rays
center of a convex lens will leave the
lens traveling in the exact same
direction.
•2 •F
F
•F 2F
•
Convex Lens: Object Beyond 2F
object
•2F
•F
•F
image
•2F
The image formed
when an object is
placed beyond 2F
is located behind
the lens between F
and 2F. It is a real,
inverted image
which is smaller
than the object
itself.
Optics Problems
Equations:*
* Refer to your Optics Reference Sheet
An object stands a distance of 36 cm
from a concave mirror. An image forms
18 cm from the mirror.
What is the focal length of the mirror?
An object stands a distance of 36 cm
from a concave mirror. An image forms
18 cm from the mirror.
What is the center length of the circle?
An object stands a distance of 36 cm
from a concave mirror. An image forms
18 cm from the mirror.
What is the magnification factor of the
image?
An object stands a distance of 36 cm
from a concave mirror. An image forms
18 cm from the mirror.
If the object has a height of5cm, what is the height of the
image?
An object stands a distance of 36 cm
from a concave mirror. An image forms
18 cm from the mirror.
State the relative size (bigger/smaller), orientation (upright/inverted),
and type (real/virtual) for the image that is produced.