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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 (–273C) 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 (–273C) 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