Transcript Slide 1

P1.5.4 Red-Shift
Mr D Powell
Connection
•
•
•
Connect your learning to the
content of the lesson
Share the process by which the
learning will actually take place
Explore the outcomes of the
learning, emphasising why this will
be beneficial for the learner
Demonstration
• Use formative feedback – Assessment for
Learning
• Vary the groupings within the classroom
for the purpose of learning – individual;
pair; group/team; friendship; teacher
selected; single sex; mixed sex
• Offer different ways for the students to
demonstrate their understanding
• Allow the students to “show off” their
learning
Activation
Consolidation
• Construct problem-solving
challenges for the students
• Use a multi-sensory approach – VAK
• Promote a language of learning to
enable the students to talk about
their progress or obstacles to it
• Learning as an active process, so the
students aren’t passive receptors
• Structure active reflection on the lesson
content and the process of learning
• Seek transfer between “subjects”
• Review the learning from this lesson and
preview the learning for the next
• Promote ways in which the students will
remember
• A “news broadcast” approach to learning
Mr Powell 2012
Index
PRAC Ideas...
•
•
•
•
•
•
•
reflecting light off a plane mirror at different angles
using a class set of skipping ropes to investigate
frequency and wavelength
demonstrating transverse and longitudinal waves with a
slinky spring
carrying out refraction investigations using a glass block
carrying out investigations using ripple tanks, including
the relationship between depth of water and speed of
wave
investigating the range of Bluetooth or infrared
communications between mobile phones and laptops
demonstrating the Doppler effect for sound.
Name these pictures then...
Which is;
1.
2.
3.
4.
The furthest away?
outside the Milky Way galaxy?
largest?
not affected by the Sun’s gravity?
Mr Powell 2012
Index
P1.5.4 Red-Shift – Expanding Universe P6.4 p100
a) If a wave source is moving relative to an
observer there will be a change in the
observed wavelength and frequency. This
is known as the Doppler effect.
b) There is an observed increase in the
wavelength of light from most distant
galaxies. The further away the galaxies are,
the faster they are moving, and the bigger
the observed increase in wavelength. This
effect is called red-shift.
c) How the observed red-shift provides
evidence that the universe is expanding
and supports the ‘Big Bang’ theory (that
the universe began from
a very small initial point).
Mr Powell 2012
Index
The Constellations

Stars which are far away Suns appear to be fixed in
the sky and over time have been named the
constellations due to their patterns. These patterns
have changed over thousands of years but not
appreciably in our lifetimes. The Planets appear to
wander across the sky as they orbit in the solar
system. Cosmological objects also vary in
brightness
TASK: Can you draw
out a couple of
examples of
constellations and
explain why the
sky looks the way it
does when viewed
from Earth. Use
the text to help
you.
C-E
Mr Powell 2012
Index
Our Place in the Universe
You in Calverton!
Mr Powell 2012
Index
Formation of the Universe
Although people often believe that a god created the
world, current scientific experts have come up with a
theory for creation called the big bang which has
scientific proof!
This theory involves a great explosion where
everything in the known universe was formed. All the
energy and matter found today in the universe
expanded from tiny point and formed the galaxies,
stars, planets, asteroids, gases, dust and energy.
TASKS
Can you construct and
storyboard this
information into a
pictorial
representation
C-D
Even today the universe is still expanding. In fact one
example of how we can prove this is by looking at a
phenomenon called red shift.
It was discovered by accident that light emitted from
stars in other galaxies seemed to be shifted more
towards the red end of the spectrum than expected.
i.e. when we expected violet light we actually got blue!
Mr Powell 2012
Index
Wavelength....
To understand this we need to understand why we
see colour?
Coloured light relates to a certain wavelength or
frequency of the EM radiation between 400-700nm.
The reason the “Red shift” occurs in light travelling
from far away is because the wavelength of the light
gets a little longer because as the light travels very
C
TASKS
long distances the wavelength gets stretched as the
universe expands!
1. Draw out a copy of the
The reverse effect happens when ambulances sirens
diagram in colour
sound higher pitch when it is coming towards you.
2. Explain the concept by
The sound waves are compressed by the motion,
using a star travelling
and the wavelength decreases. Remember that red
towards you and one
light has a longer wavelength than
away
blue.
Mr Powell 2012
Index
Use of Emission Spectrums?
• How do we know which elements stars are made up from?
• How do we know the age of stars?
• Scientists can begin to answer these questions once they have an
understanding of line spectra.
Mr Powell 2012
Index
What are we talking about?
• When we talk about “Line Spectra” for an atom we simply
mean that an atom can absorb or emit radiation at certain
frequencies. If we look at the frequencies emitted or
absorbed we can see a spectrum with omissions.
656nm
Mr Powell 2012
Index
How are they made?
 There are three types that you might see....
Mr Powell 2012
Index
Other Elements Emission Spectra....
Mr Powell 2012
Index
Spectral Gases
Image we look towards a star and then pass its light through a cold gas then
then a prism to make an absorption spectrum what elements would be present?
Star X
Mr Powell 2012
Index
Spectral Gases & Shift
Here are three spectral diagrams from a star. The first one is a reference diagram.
The second two are shifted across to the red end of the spectrum. Hence, they are
moving away from us. We can tell how fast they are moving by the shift. The middle
band is actually shifted by a distance of 100Å (angstrom) or 100 x 10-10 m. (10nm).
This translates to a speed of 24,000 km/hour or 15,000 mph. The bottom band is
shifted by 760Å or (76nm) which translates to a speed of 136,000km/hour or 84,000
mph.
Mr Powell 2012
Index
Spectral Gases Conclusion
So these pictures show us that the lower stars are moving away from us
Also the further they are away the faster they travel.
Mr Powell 2012
Index
Quick Questions...
The figure shows two identical
galaxies, P and Q, in the same
photograph.
P
Q
1. Which galaxy is nearer?
2. Which galaxy would have the
larger red shift?
3. Which galaxy is moving away
faster?
Mr Powell 2012
Index
Summary Questions....
Copy & Complete
spectrum Each colour has a
White light is made up of the colours of the visible _________.
wavelength When this light is passed through a gas certain
different ____________.
spectra
absorbed the patterns produced are called ________:
wavelengths are __________
away from us we would find that the absorption
If the light source is moving ______
shifted towards the _____end
red
lines are all _______
of the spectrum (the longer
faster the light source is moving the further its pattern is
wavelength end). The ______
universe also shows this pattern, so we
shifted. Light from the edge of the _________
assume that the edges of the universe are all moving away from a single point.
Big Bang theory.
This is called the _________
Words to use: shifted, red, spectrum, Big Bang, absorbed, wavelength, absorption
spectra, away, universe, faster
Mr Powell 2012
Index
P1.5.4 Red-Shift
P6.5 The Big Bang p 102
d) Cosmic microwave
background radiation (CMBR)
is a form of electromagnetic
radiation filling the universe. It
comes from radiation that was
present shortly after the
beginning of the universe.
e) The ‘Big Bang’ theory is
currently the only theory that
can explain the existence of
CMBR.
Mr Powell 2012
Index
The Horn Antenna

In this next task you will have watched the video clip
about the Horn Antenna and seen a series of text clips
like the one to the right. Use these to help you answer
the following questions.
1.
Explain, as fully as you can, why the frequency profile of
electromagnetic radiation is an indication of
temperature.
2.
Describe, in as much detail as you can, what cosmic
microwave background radiation is and how it was
discovered.
3.
Explain, as fully as you can, how cosmic microwave
background radiation fits in with the idea that the
Universe, as it now is, began with a big bang.
4.
Some people think that Penzias and Wilson’s discovery
of cosmic microwave background radiation was just
lucky. Others disagree. What do you think? Give reasons
for your answer.
A*-D
A) Microwave “noise”
reaches Earth with almost
the same intensity from
every direction. It is called
cosmic microwave
background radiation.
Mr Powell 2012
Index
HSW
2
A) Microwave “noise”
reaches Earth with almost
the same intensity from
every direction. It is called
cosmic microwave
background radiation.
1
D) Bodies which emit
radiation do so across
a range of frequencies,
as shown on the graph.
B) All bodies with a
temperature above
zero kelvin (–273C)
emit EM radiation.
E) Radiation in the
microwave region of
the electromagnetic
spectrum reaches
Earth from many stars
and galaxies.
1
3
F) In 1965, the astronomers
Penzias and Wilson stopped trying to
eliminate “noise” from their
2
microwave detectors and studied it
instead.
2
G) The frequency at which a
body radiates most energy(
fmax) is directly proportional
to the kelvin temperature. 1
I) Because of the expansion of the
Universe, the temperature of radiation
from the time of the big bang will now be
3
only a few kelvin.
C) Measurements made by the
COBE satellite showed that there
are very slight “ripples” in the
cosmic microwave background
radiation.
H) Cosmic microwave background 3
radiation has an energy profile
matching a temperature of 3 kelvin
(–270  C).
J) The early universe could not have been
completely uniform otherwise galaxies would
never have formed.
3
Mr Powell 2012
Index
The Horn Antenna
A) Microwave “noise”
reaches Earth with almost
the same intensity from
every direction. It is called
cosmic microwave
background radiation.
D) Bodies which emit
radiation do so across
a range of frequencies,
as shown on the graph.
B) All bodies with a
temperature above
zero kelvin (–273C)
emit EM radiation.
E) Radiation in the
microwave region of
the electromagnetic
spectrum reaches
Earth from many stars
and galaxies.
G) The frequency at which a
body radiates most energy(
fmax) is directly proportional
to the kelvin temperature.
I) Because of the expansion of the
Universe, the temperature of radiation
from the time of the big bang will now be
only a few kelvin.
C) Measurements made by the
COBE satellite showed that there
are very slight “ripples” in the
cosmic microwave background
radiation.
F) In 1965, the astronomers
Penzias and Wilson stopped trying to
eliminate “noise” from their
microwave detectors and studied it
instead.
H) Cosmic microwave background
radiation has an energy profile
matching a temperature of 3 kelvin
(–270  C).
J) The early universe could not have been
completely uniform otherwise galaxies would
never have formed.
The Horn Antenna – Mark the work...
1) answer includes items: 3 B D G
each for 1 mark
2) answer includes items: 3
A E F [allow H here for a further mark]
each for 1 mark
3) answer includes items: 4 C H* I J
each for 1 mark [*unless already credited in (2)]
A*-D
A* = 10
A=8
B=6
C=4
D=3
4) ideas that:

lucky in the sense that they weren’t initially looking for the
background radiation [others were!!!]
 more than just lucky in that they investigated it and
 didn’t just ignore it
each for 1 mark
[NB Reference to letters only, not a prose answer, gain only ½ mark
each. Total rounded down]
Mr Powell 2012
Index
Plenary free writing....
In the past two lessons you have completed work relating
the start of the known universe. Answer the
questions below which relate to both lessons...
Describe two pieces of evidence which relate to
microwave radiation and visible light which suggest
out universe started from a singularity (single point)
and is expanding and cooling as it expands.
Follow the following key points for each one;
1.
2.
3.
4.
Name the process
Describe what the mechanics of the processes are
Explain their significance with respect to the formation
of the Universe
Suggest why this conflicts with belief about the creation
of the Universe and Earth in the Bible. (Science in
Society)
Mr Powell 2012
Index