Radiation & Telescopes
• ____________
radiation: Transmission
of energy through
space without physical
connection through
varying electric and
magnetic fields
• Example: __________
Wave Motion
Label the Wave
How we see light video
_____________: Number of wave _______ that
pass a given point per second
__________: Time between passage of
successive crests
Relationship:
Period = 1 / Frequency
Wavelength: ___________ between
successive _________
Velocity: __________ at which crests move
Relationship:
Velocity = ____________ / ________
No limit on
wavelengths;
different ranges
have different
names
Note opacity of
atmosphere
Light and
Color Bill Nye
Video Part I
Waves
The Speed of Light in Glass Video
• Water waves, sound
waves, and so on,
travel in a ________
(water, air, …)
• Electromagnetic
waves need ____
____________
• Created by
accelerating
_________ particles
What is the wave speed of electromagnetic
waves?
c = 3.0 x 108 m/s
This speed is very large, but still finite; it can
take light __________ or even __________ of
years to traverse astronomical distances
Telescopes
• ____________ lens
Images can be formed through reflection or
refraction
_____________ mirror
Modern telescopes are all
_______________:
• Light traveling through lens
is refracted differently
depending on ____________
• Some light traveling
through lens is absorbed
• Large lens can be very
_________, and can only be
supported at edge
• A lens needs two optically
acceptable surfaces; mirror
needs only one
Types of reflecting telescopes
The Keck telescope
a modern research telescope
The two 10-m telescopes of
the Keck Observatory. (b)
Artist’s illustration of the
telescope, the path taken by
an incoming beam of
starlight, and some of the
locations where instruments
may be placed. (c) One of
the 10-m mirrors. (The odd
shape is explained in
Section 5.3.) Note the
technician in orange
coveralls at center. (W. M.
Keck Observatory)
Sunrise on Mauna Kea in June
The _______ Space Telescope has a variety of
detectors
Hubble Telescope image before and
after it was fixed
Here we compare the best ______________
image of M100, on the left, with the ______
images on the right
Size
• _________________ power: Improves detail
• Brightness proportional to square of radius of mirror
• Photo (b) was taken with a telescope twice the size
of the telescope that took photo (a)
Size
• Resolving power:
When better, can
distinguish
objects that are
closer together
• Resolution is
proportional to
wavelength and
inversely
proportional to
telescope size—
bigger is better!
Figure 5-12. Detail becomes clearer in the
Andromeda galaxy as the angular
resolution is improved some 600 times,
from (a) 10’, to (b) 1’, (c) 5”, and (d) 1”.
(Adapted from AURA)
Atmospheric ___________ is due to ______
movements
Solutions:
• Put telescopes on _____________,
especially in __________
• Put telescopes in _________
•Why is it Dark at Night video
________ telescopes
• Similar to optical
reflecting telescopes
• Prime focus
• ______ sensitive to
imperfections (due to
______ wavelength);
can be made very
_______
•Largest radio
telescope is the 300m dish at _________
________ wavelength means
________ angular resolution
Advantages of radio
astronomy:
• Can observe ____ hours a
day
• Clouds, rain, and snow
_______ ____________
• Observations at an entirely
____________ frequency; get
totally different ____________
Space Based
Infrared radiation
can produce an
image where
visible radiation
is __________;
generally can use
optical telescope
mirrors and
lenses
_________ telescopes
can also be in space;
the image on the top
is from the Infrared
Astronomy Satellite
The __________ Space
Telescope, an
___________ telescope,
is in orbit around the
Sun. These are some of
its images.
Ultraviolet observing
must be done in ______,
as the atmosphere
absorbs almost ______
_____________ rays.
________ image of
___________ remnant
__________ rays cannot be
____________ at all; images
are therefore __________
Full-Spectrum Coverage
Figure 5-36. Multiple
Wavelengths The Milky
Way Galaxy as it
appears at (a) _____,
(b) infrared, (c) ______,
(d) X-ray, and (e)
____________
wavelengths. Each
frame is a panoramic
view covering the entire
sky. The center of our
Galaxy, which lies in the
direction of the
constellation Sagittarius,
is at the center of each
map. (NRAO; NASA;
Lund Observatory; MPI;
NASA)