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AS and A Level: Waves & Cosmology

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  1. 1 When a source of waves is moving relative to an observer (either towards or away) the received waves have a different wavelength to the wavelength transmitted. This is known as the Doppler Effect and we can use it to calculate the speed of a galaxy relative to Earth.
  2. 2 Almost all galaxies show redshift, meaning that the wavelength received on Earth is longer than it was when transmitted. It’s called redshift because the wavelength received has moved towards tor even beyond the red end of the spectrum . Redshift implies that the galaxy is moving away from Earth.
  3. 3 Blueshift can be observed from ‘nearby’ stars and galaxies.

Hubble's law

  1. 1 Using redshift data from a number of galaxies, Hubble plotted a graph of recession velocity, v, against distance to the galaxy, d. This graph continues to be updated and it shows that v = Hod which is known as Hubble’s law. This means that the speed of recession is directly proportional to the distance to the galaxy.
  2. 2 Ho is the Hubble constant and it has a value of about 70 km s-1 Mpc-1, which is equivalent to 2.3x10-18 s-1. 1/Ho= 4.4 x1017 s = 1.4 x 1010 years! This is the age of the universe, about 14 billion years.
  3. 3 We can also find an estimate for the size of the (visible) universe, assuming that the maximum expansion speed is the speed of light. Using Hubble law, c = Hod so d = c/Ho = 14 billion light years.
  4. 4 The uncertainty over the value of The Hubble constant is becoming smaller as measurements of distance to galaxies improve
  5. 5 Since redshift is seen in every direction, the conclusion is that the universe is expanding.

Fate of the universe

  1. 1 The fate of the universe is closely linked to CRITICAL DENSITY. This is a theoretical density that would have enough mass in the universe to keep the expansion of space slowing down forever. The critical density is given by o= 3H2/8 . The universe would be FLAT. An accurate value for H is important, if we want an accurate value for the critical density. Note: H2 means that the percentage uncertainty in H has to be doubled.
  2. 2 If the actual density is greater than the critical density, then the universe will stop expanding at some point and then collapse. The universe is then CLOSED. This outcome is known as the Big Crunch.
  3. 3 If the actual density is less than the critical density, there is not enough mass to stop the expansion and the universe will continue to expand forever. The universe is OPEN.
  4. 4 Determining the actual density is difficult because there seems to be dark matter which we cannot yet detect directly but which can be inferred by the gravitational effects it has. e.g the rotation of galaxies is not consistent with observable mass but with increased mass that may be explained by the presence of dark matter.

  • Marked by Teachers essays 2
  • Peer Reviewed essays 20
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  1. Marked by a teacher

    Wavelength of red light

    3 star(s)

    The grating causes the concentrated light to break up again. Maxima occur on the screen where the light is in phase. The dot in the centre is called central maximum or 0th order spectrum. The next dots left and right from the central maximum are called 1st order spectrum; the next ones are called 2nd order spectrum and so on. The measurements 1. Set up the equipment 2. Cut the graph paper into 4 stripes and glue them together to get one long stripe 3. Stick the long stripe with blue tack on the wall 4.

    • Word count: 806
  2. Peer reviewed

    Radio Waves

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    In the 1888, German physicist Heinrich Hertz proved Maxwell's theory by discovering long- wavelength radio waves and confirmed it in his book, "Investigations on the Propagation of Electrical Energy". In his experiment, an induction coil producing high voltage was connected to a metal pedestal where a spark produced electromagnetic waves that reached the resonator. Here, an electric current was produced and formed a spark in the spark gap that helped Hertz detect the radio waves. Consequently, Hertz's discovery of the radio waves sparked new inventions and technologies.

    • Word count: 580
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    Investigate the factors which will effect the stretching of a Helical Spring when put under a load.

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    If the experiment is correctly done, the law should show to be true. Prediction: I predict that the greater the weight applied to the spring, the further the spring will stretch. This is because extension is proportional to load and so if load increases so does extension and so stretching distance. Equipment: * 25swg Copper * 26swg Nichrome * 32swg Constantin * 32swg Nichrome * Stand * Clamp * Ruler * Weights * Hook Method Step 1: Collect all equipment Step 2: Set-up as diagram below shows. Step 3: Get a Copper wire, and using a cylindrical object (same size all the time), wrap around to create a spring.

    • Word count: 930
  4. Peer reviewed

    Universe - Definitions

    Pulsars These are neutron stars that emit an enourmous amount of radiation. They spin hundreds of times a second and we pick up the radio waves on Earth. Neutron Stars Formed from very large stars collapsing. Between 10 and 100 km in diameter a they can have a mass many times that of the sun.

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  5. Peer reviewed

    Electromagnetic spectrum facts.

    * In a vacuum, all e-m waves travel at (approximately) 300 million metres per second (3 x 108m/s) - the fastest speed in the universe. * When e-m waves travel through matter (for example, light through air or glass), they travel a bit slower than this but rarely less than half as fast as in vacuum. * Waves of different frequencies travel at different speeds in transparent matter - so a mixture of waves can be separated out by diffraction. For example, white light is split up into a mixture of colours when it goes through a prism. The electromagnetic spectrum table This table is nearly all you need to know about the e-m spectrum on one page.

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  6. Discharge Tubes

    APPARATUS * Power pack * Two plug-plug leads * One set of discharge tubes(with varying pressures) * Induction coil * Two plug-clip leads METHOD 1. Attach the induction coil to the power pack using the two plug-plug leads. Adjust the points on the induction coil to obtain a continuous spark from the coil. Switch off the power pack. 2. Set the power pack at the 6 volts and turn it on. 3. Attach the negative terminal of the induction coil to the cathode of the discharge tube marked with the highest pressure (50 mm Hg)

    • Word count: 570
  7. Solar cells

    For example if it is moved four times, closer the solar cell will be 4 times more powerful. However if the Solar cell is moved four times further away then the current would of decreased and then stopped. Scientific Reason for Prediction I think this because if the power source is moved closer the light intensity will increase causing the current inside the Solar Cell also to increase. Apparatus Variables Variables How it will affect my results How will I control/measure it?

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  8. Polarisation - what is it and what is it used for?

    The alignment of these molecules gives the filter a polarisation axis. The polarisation axis is across the length of the filter and only allows waves that are parallel to the axis to pass through. For instance, a Polaroid filter with its long chain molecules aligned vertically will have a horizontally aligned polarisation axis and will block all vertical vibrations and will only allow the horizontal waves to be transmitted. When an unpolarised light ray strikes the surface of a transparent medium such as water, the refracted ray is partly polarised and at most angles the reflected ray is also polarised.

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  9. To what extent are coastal landforms products to marine processes?

    In addition one of the four processes listed above might have a bigger impact on a coastal landform than the others. Waves, currents, tides, salt sprays and some biotic features like corals are all known as marine processes. The waves supply a huge amount of energy that results erosion of the land and the deposition of the eroded sediment on the coast. Formed by the friction between the wind and the surface of the water, the wind waves that are in deep sea are waves of oscillation and the ones that are in shallow water are waves of transition.

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  10. Does an elastic band behave in the same way as a steel spring?

    We recorded the results of the length in cm at the pointer, each time a weight was added or removed and at the beginning and end when no force was being applied to the elastic band. We repeated the experiment 3 times to make sure our results were valid. We made sure the experiment was fair by keeping the following variables the same; Elastic band Apparatus Units on metre rule to record results (cm)

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  11. Develop & Update Tourism Industry Knowledge.

    Hotel facilities include a cocktail bar, a cater restaurant, guest laundry, dry cleaning and 24 hours reception. 4 stars hotels (First Class Hotel) Rydges Melbourne is a 4 stars hotel located in the CBD it offers a charming, modern and warm rooms with individual reverse-cycle air conditioning, television, modem line, in-house movies, refrigerator and tea/coffee, mini bar and video facilities. Hotel facilities include a CBD Caf� Bar Restaurant, entertainment lounge, 24 hours reception and room service, express checkout, conference facilities, rooftop heated pool, dry cleaning and valet services.

    • Word count: 685
  12. Investigate the factories, which affects the extension of a metal spring.

    The greater the force will be the greater the extension will be. 4. the material of the spring will affect the extension because different materials got different strength Prediction: I predict that the extension will be proportional to the stretching force so long as the string is not permanently stretched. This means that the results should be near enough consistent while increasing in the extension until I reach the end of the experiment. Safety Precautions: I am going to make my experiment safe by wearing safety goggles, just in case the spring breaks and bounces back to my eye.

    • Word count: 922
  13. The Investigation was about how waves travel.

    What are all the things we will measure? We will count how many waves will travel along the tray and also time it, when the waves slow down and finally stop we will stop the clock How will you make it a fair test We made it a fair test by measuring the force of push accurately by using a ruler. Keeping the 2000 ml volume of water How will I be safe? We were safe by moving all chairs and stools away from our area.

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  14. In this investigation I am trying to find out how a spring behaves and if I double the ammount of springs I double the average extension pull.

    Prediction I predict that as the force in Newton increases the extension (mm) will increase. This is because there is greater force acting on the spring. The data I collected from my preliminary work can help me to predict that if the number of springs doubles the average extension per spring will also double. I found out that the average extension pull on the spring at 1N = 36mm this means the average extension pull on 2 springs should be 72mm and so on. This is because springs in series will always be direct proportion.

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  15. Investigation into Hookes Law - investigate the effect of mass on the extension of a spring.

    * Spring Diagram: Fair Test: I will try to keep this a fair test by only investigating 1 variable. So these are the things that will stay the same through out the experiment: * The Thickness of the spring * The length of the spring * The material of the spring The things that will vary throughout the experiment will be the mass and the extension. But I will only investigate and vary the mass myself because the extension will change as a cause of the mass being changed. This test will be kept fair by using the same weights making sure they are all 50 grams and I will place them on the spring carefully and wait to measure it when the spring has stopped moving.

    • Word count: 997
  16. Prove if Hookes Law's theory of extension is proportional to length is true.

    Step-by-Step instructions: * Clamp head to stand, * Connect boss head to clamp, * Fix one circular up to other, * Hook weights up to the spring * Add weights then record extensions after measuring it three times, * Do this with eight different weights, * Record extension from original length after finding out the average. Apparatus: The equipment that will be required for the testing of Hookes Law is: * Clamp and Stand * Weights 50grams each * A measuring apparatus (preferably a 1 meter ruler)

    • Word count: 930
  17. Carry out a two source superposition of laser light experiment using a double slit, and determine the wavelength.

    * Markings are made on the graph paper showing where bright fringes are. * The distance(d) between the double slit and the screen is measured using metre rulers. * The distance across a number of fringes is measured with a normal ruler to determine the fringe spacing(x). Results Nine bright fringes were produced on the screen. To calculate the fringe separation, the length across a number of bright fringes is divided by the number of dark fringes separating them. 4.5 = 0.5625cm 8 = 0.005625m Treatment of Results There is now enough information to determine the wavelength of the laser using the following equation: ?

    • Word count: 930
  18. An Investigation To See If Hookes Law Is Or Is Not reliable.

    I believe each 100g weight will move the spring in equal or round about additions each time i.e. 100g = 1cm extension 200g a further cm or 2 etc. Factors: Factors that may affect this experiment are: * A moving spring * Spring passing yield point * Measuring from same point each time All these may or will affect the results of my experiment and alter the outcome in my conclusion. All these should and will be kept a constant. Apparatus: * A spring * Boss and Clamp * 30cm ruler * 100g weights Diagram: Method: * For safety measures I will stand up during the whole experiment * For fairness I will keep all the above factors a constant and use the same spring throughout.

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  19. "Naked Ed".

    We contemplated ignoring the small canal that would take us to the exceptional and stunning spring, but being the explorers we are, we decided to give the spring a go. As we approached the spring, the first object I noticed was the straw hut on stilts. Next, I noticed a man sitting on a small dock built off of the hut. As we paddled ashore, I instantly felt comfortable because of the shouts of welcome I heard from Naked Ed.

    • Word count: 729
  20. Investigate Hooke's law, using masses and springs.

    I will use 100g weights because anything smaller would take too long to do and anything bigger would be too heavy and the spring would reach its LOP (limit of proportionality) too quickly. Apparatus 1 X Lump of plasticine 1 X Mass holder 1 X Meter ruler 1 X Clamp 1 X Boss 1 X Spiral spring 1 X Retort stand 1X Paper clip 1 X Large weight And a collection of 100g discs. Method I set up my apparatus as shown in fig 1.

    • Word count: 979
  21. Investigating Hook's Law.

    The searching could be small because the atoms of solid are tightly packed together. The Kind of force used to observe the extension of spring after masses has been applied is known as potential force. When the potential force has been applied, one end and suspend sequence of masses are fixed to measure the spring extension. Aim: To observe if an extendable spring obeys hook's law. Prediction: When applying masses expands a spring it will go back to its normal shape in order to obey the hook's law. Apparatus *Clamp *Clamp Stand *Ruler *Hangar *Slotted Mass *Spring *Celotape.

    • Word count: 746
  22. The aim of my investigation is to see how each spring has been affected each time you add on a 100g on a spring.

    I will then add weights to the spring and measure extension. As I am doing this, I will record my results in a table. I will continue to do the tests until the spring will not return to its original shape. To make the tests fair I will use the same spring and set of weights each time. Also I will add the weight proportionally in 1 Newton (10kg) each time. Therefore the change in weight will remain the same.

    • Word count: 796
  23. The aim of this investigation is to ascertain the effect of weight on a child's toy in relation to how high it will bounce.

    This way you get w.d. = Force x Compression. Then, to find out the energy stored in the spring, you need to know the area under the line when it is plotted on the graph, like in the example below: To find out the area, the equation is 1/2 x base x height. This makes the equation for the amount of energy stored in a spring 1/2 x force x compression. The force and the compression on the spring in this toy will always be the same, more or less.

    • Word count: 566
  24. Qur'an on origin of the universe.

    This barrier divides the two seas so that each sea has its own temperature, salinity, and density.1 For example, Mediterranean sea water is warm, saline, and less dense, compared to Atlantic ocean water. When Mediterranean sea water enters the Atlantic over the Gibraltar sill, it moves several hundred kilometers into the Atlantic at a depth of about 1000 meters with its own warm, saline, and less dense characteristics. The Mediterranean water stabilizes at this depth.

    • Word count: 584
  25. Movement analysis project - The skeletal system.

    Physical activity is achieved as a result of over 600 muscles that contract or shorten, thereby facilitating the movement of the skeleton across its joints. Muscles are the converters of energy. 3. Name the insertion, origin and state the functions of the following muscles. Muscle Function Insertion Origin Pectoralis major Flexes upper arm and adducts upper arm Humerous Sternum Clavicle Rib cage Latissimus Dorsi Extends upper arm Adducts upper arm Humerous Vertebra (T6-L5) Deltoid Flexes upper arm Adducts upper arm Extends upper arm Humerous Clavicle Scapula Acromion Biceps Brachi Flexes lower arm Radius Scapula Triceps Extends lower arm Oclearanon Humerus

    • Word count: 767

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