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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

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    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. Marked by a teacher

    Wave Coursework

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    This will also increase the reliabilty of my results. I will then be able to work out an average, removing any error results out of limit. Before taking any readings of the wave velocity I will measure the length and width of the tray and also see if the tray is flat on the bottom and along the sides. I will do this by placing 1cm depth of water into the tray, taking the measurements at either end and in the centre of the tray.

    • Word count: 1223
  3. Peer reviewed

    Black Holes Research and Report

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    As the name implies, a blackhole cannot emit or reflect any light; making them practically invisible. If enough mass is concentrated into a small enough region, the curvature of space-time becomes so harsh that nothing can continue to orbit stably; not even light. The ultimate fate of all incoming matter is to be destroyed in a singularity, a region of infinite density. The interior of a black hole is poorly understood because no form of information can ever leave. However new technologies are allowing us to receive a new phenomenon called hawking radiation, so this may be true for only a short period of time.

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  4. 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.

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    Annihilation Theory

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    Matter and antimatter is a collective term given to two identical particles that are of opposite charge. Therefore they are the same with the exception of charge. There opposite charges adhere to the Laws of Attraction, which state that two particles of opposing charge are attracted to each other. On their collision they, theoretically, annihilate each other resulting in a gamma ray (pure radiation). This can be shown by; e+ + e- � ? (A positron plus and electron results in a gamma ray) Equations like these show the fundamental properties of all interactions. Here, the resultant is a gamma ray, which indicates that (considering that gamma particles travel at the speed of light)

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    What affects the voltage output of a solar panel?

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    measure the diameter of the light bulb and hence calculate the distance between the point source to the solar cell Wires Used to connect the ray box to the power pack and the voltmeter to the solar cell Ruler Used to measure the distance between the point source and the solar cell A ray box is chosen over a light bulb as the light bulb will emit light out of all directions, while the ray box's light can be controlled to be emitted out through one direction, to the solar cell.

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    The Electro magnetic spectrum.

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    Their wavelength is usually a couple of centimetres. Stars also give off microwaves. Microwaves cause water and fat molecules to vibrate, which makes the substances hot. Thus we can use microwaves to cook many types of food. Mobile phones use microwaves, as they can be generated by a small antenna, which means that the phone doesn't need to be very big. The drawback is that, being small, they can't put out much power, and they also need a line of sight to the transmitter.

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  8. Peer reviewed

    Investigate the effect of mass on the extension of a spring.

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    * Boss Clamp Hypothesis Using scientific knowledge from that of Hooke's law, I am able to conduct a hypothesis. Hooke's law reveals that the extension is proportional to that of the load, and so if load increases, so does the extension and so stretching the distance. He discovered that extension is proportional to the downward force acting on the springs and so we can use this formula to predict the results. Extension= New length - Original Length 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 To see if my prediction is correct I will experiment, and obtain results using Hookes Law.

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  9. Peer reviewed

    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.

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    The effects of the extension of a spring on the time it takes a weight to oscillate.

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    So therefore: 1/2 mv2 = maX 1/2 mass x velocity2 = mass x acceleration x extension (distance) The velocity value is the velocity at the mid point which is where the mass final comes to rest after oscillating. The formula can be simplified to: v2 = 2aX Velocity is distance/time and acceleration is force/mass therefore with substituting the formula is: (distance/time)2 = 2 x (Force/Mass) x X Which is equal to: (time2 / distance2) = mass / 2 x force x X The values on the top half of the formula are the constants in this experiment.

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    A report concerning stars and constellations

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    Even the Bible makes reference to this famous group. God, while pointing out how all-powerful he was, is purported to have asked Job if he (Job) was able to "loose the bands of Orion" Leo (Lion) The first on the list of Heracles' labours was the task of killing the Nemean Lion, a giant beast that roamed the hills and the streets of the Peloponnesian villages, devouring whomever it met. The animal's skin was impervious to iron, bronze, and stone. Heracles' arrows harmlessly bounced off the lion; his sword bent in two; his wooden club smashed to pieces. So Heracles wrestled with the beast, finally choking it to death.

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    Investigation on whether Rubber obeys Hooke's Rule

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    The return is elastic. Hypothesis I predict that the greater the weight applied to the rubber band, the further the rubber band will stretch. This is because, according to the findings of Hooke's Rule, the extension is directly proportional to the load (i.e. tension force). So if the load increases (i.e. the tension increases), then the extension increases. Furthermore, I think that doubling the load (doubling the tension force), will double the extension. However, the rubber band will reach its elastic limit where the extension will continue to increase, but not increase in proportion to the load due to unusual temperature changes and weaker forces of attraction.

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    See how one factor affects the period of time a mass on the end of a spring takes to complete one whole oscillation.

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    I have chosen to make mass the variable, as this is the easiest variable to use in this experiment. Equipment Here is a diagram of the equipment I will use: Method This is how I will carry out the experiments: 1. Set up the equipment as shown in the diagram 2. Put the mass on the end of the spring (see below for range) 3. Measure the initial displacement (see below) 4. Time 10 oscillations, and divide this answer by 10.

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    Properties of Waves.

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    Reflection can be used to guide a laser past obstacles to a receiver. Shiny surfaces such as mirrors are smooth so reflect all light strongly as all the waves pass in one direction only. Rough surfaces look dull as they reflect light in many different directions causing it to scatter. This is called diffuse reflection. If light waves are reflected, the colour of the surface affects the colour of the reflected ray. Concave surfaces are used to focus waves at a point to increase their strength, for example satellites collect radio waves in a dish, then focus the waves on to a point.

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    Astronomy - the urge to explore space.

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    It was also found out that the building door and the main door were at an angle of 20�. Astonishingly, this is the exact angle that the same two stars of the constellation had on each other. Until the 11th century the truth about the stars was unknown and there were just a few theories of Ancient Greeks. In the 11th century an Arab astronomer presented the hypothesis of the stars being a lot bigger mass than they appear to the naked eye. This theory was a great new discovery for the astronomers from all over the world and it opened a new era for the astronomers of the future.

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    The Electromagnetic Spectrum

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    Radio waves are picked up when they hit the antenna of the radio telescope. The wave then goes to the tuner, then to the amplifier, and finally to the plotter. ? For Consumer Goods - these waves are used in the remote control models which people buy. They are also used in radios, televisions and wireless headphones. The antennae on your television set receive the signal, in the form of electromagnetic waves that is broadcasted from the television station. It is displayed on your television screen. Celestial bodies that transmit radio waves: Karl Jansky was the first to determine that radio emission from the heavens could be detected.

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    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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    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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  19. Peer reviewed

    The Electromagnetic Spectrum.

    X-rays are also very high-energy waves and can be dangerous when exposed to them for long periods of time. Gamma waves are less than 10 trillionths of a meter and are even more penetrating then X-rays. The electromagnetic spectrum is not only measure in wavelengths. It is also measured in frequency (cycles per second known as Hertz) and energy involved (measured in electron volts) Objects in space, such as planets and comets, giant clouds of gas and dust, and stars and galaxies, emit light at many different wavelengths. Some of the light they emit has very large wavelengths - sometimes as long as a mile!.

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  20. Resonance in a Closed Air Column Investigation.

    The sound emitted by each tuning fork is: 2. The speed of the waves using the universal wave equation, for each tuning fork is: 3. The wave speed of the first tuning fork was faster than the wave speed of the second tuning fork. I am surprised because the frequency of the first tuning fork was higher than the frequency of the second tuning fork. According to, the universal wave equation, . This means that when frequency increases wavelength decreases.

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  21. Is Space Exploration Worth the Cost?

    For example space exploration allows the prediction and management of hurricanes and other natural disasters. Without this many people would suffer from the devastating effects of natural disasters and would not have the opportunity to evacuate an area before a disaster occurred. Important medical developments such as breast cancer detection and biopsy systems, ultrasound scanners and cataract surgery tools have also developed from space technologies. Solar energy, a key alternate energy source to unsustainable fossil fuels, is another technology that has advanced from space [2]. Tax dollars spent on space projects result in jobs, a large proportion of which are high paying, high tech positions.

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  22. The aim of my coursework is to calculate the wavelength of red laser light using the diffraction grating formula and the Youngs double slit formula.

    Insert the 300mm diffraction grating into the slit holder. 4. Place the diffraction grating with the slit holder, 2 meters away from the screen which in my case was a white wall. 5. Mark the spectrum on the wall with a pencil. 6. Measure the length of the distance between the fringes. 7. Take away the diffraction grating and replace it with the double slit. Also remove the two lenses. 8. Repeat the process until all measurements are taken with all the different slits.

    • Word count: 1437
  23. Refractive index by tracing light rays

    A sheet of paper was fixed on the drawing board and the glass block was placed in the middle. The outline of the glass block was sketched by using a sharp pencil. 2. The glass block was removed and 5 straight lines were drawn to represent light rays with angle of incidence varying from 25o to 65o as shown in Fig.1. The lines were labelled as Ray 1 to Ray 5. For each line, the normal is drawn as dotted line and the angle of incidence (i) was measured. 3. The glass block was placed back to the original position.

    • Word count: 1968
  24. Free essay

    OCR Physics B Research Project - The Expanding Universe

    Once the idea of a universal attraction between masses was introduced, people used two different ideas to justify a belief in a static universe. The first was that God held everything apart. The second was by introducing a force which opposed gravity on a large scale. When Einstein formulated his Theory of General Relativity, he introduced a force called the "cosmological constant" to fit in with his views of a stationary universe. Speculation regarding a non-eternal and expanding universe Olber's paradox, first described in 1823, suggests that the idea of an infinite universe does not fit with observational evidence.

    • Word count: 2052
  25. Our Universe as a Laboratory for Understanding Physical Laws

    A great reason why our universe is such a good laboratory is that everything is right in front of us; it is just a matter of us looking in the right direction at the right time using the right tools. A standard candle is a term used for an astronomical object, often a star, of well understood intrinsic brightness which enables us to determine cosmic distances (CAS online). If an object can be found whose luminosity you knew absolutely just from looking at it, then by comparing the apparent luminosity with the absolute luminosity, you could figure how far away it was.

    • Word count: 2065

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