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# AS and A Level: Waves & Cosmology

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## Redshift

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. ## 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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2. ## 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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3. ## The Electromagnetic Spectrum

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4. ## 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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5. ## 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.

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6. ## 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.

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7. ## Sound waves

However, in some cases, it is reflected which more commonly called as echo. When sound strikes soft materials, it is absorbed. Such materials that absorb most of the energy of sound waves are called sound insulators. This property of the sound is beneficial to geologists to locate oil reservoirs. It also helps in tracking earthquakes and to find out how earthquakes travel through different kinds of rocks and magma. Ultrasonic waves are those sound waves which are of every high frequency with short wavelengths. Though human ear cannot feel or recognize it, it has many uses.

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8. ## An investigation into the behaviour of springs inparallel when a mass is applied.

Extension a Stretching Force In my investigation I intend to investigate the extension of springs in parallel, varying in number when a fixed mass is applied. Information about the springs used in the experiment: Length of the coiled portion when closed 20mm Length of the coiled section is 60mm when a mass of 100g is attached. Max length of coiled section without permanent deformation, (elastic limit). 150mm Preliminary Experiment: The objective of the preliminary experiment is to determine the size of the load I intend to attach to the springs in my experiment.

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9. ## Investigate any relationship present between the distance between a solar cell and a lamp, and the current output of the solar cell, at a fixed voltage.

As all light travels at the same speed (300,000 m/s), we know that the wavelength of the light will determine how much energy is given out from the light. The wavelength and frequency are directly related in light, because both multiplied must give a product of 300,000 m/s. We can gather by the formula that lights with a smaller wavelength will give out more energy, because when a smaller number is divided by the wavespeed and multiplied by the constant, a higher value for the energy will be given than if a large wavelength figure is divided by the wavespeed, to give a smaller figure, which when multiplied by the constant gives a smaller amount of energy.

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10. ## An Investigation into the Factors, which affect the Voltage Output of a Solar Cell

= + From looking at the methodology of my preliminary experiment I know that there are many other variables. In my preliminary experiment my main aim was to investigate as many other variables as I could think of, which might affect the output or voltage. I did this because by considering all the other variables I am able to regulate them, keeping my experiment as fair as possible. The other variables or independent variables that I have noted from my preliminary investigation include: * Keeping the light source (lamp or ray box) the same distance from the solar cell through out all experiments that I carry out. I will place the solar cell 15cm away from the light filament.

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11. ## Making sense of data - finding a value for the young modulus of a flexxible strip of material.

The weights that are hung on one end of the ruler will vary each time by adding 50g to the previous weight and each time the deflection of the ruler is read until 450g of weights have been added. Method Arrange the apparatus as shown in the diagram. As the apparatus is fixed appropriately we can then start the experiment. As the apparatus is fixed we might see the ruler has a slight bend without any weights on it this is due to its own weight, this can be counted as a systematic error.

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12. ## The Anglers Problem

Doubled force means double the stretch. This is known as a mathematically direct relationship. Line of best fit for a force vs. stretch graph would be a straight line ascending steadily, as the weight increases. This is because the amount the spring stretches is directly proportional to the stretching force. This direct relationship can be represented by the formula: y = mx+b, where m is the slope and b is the y-intercept. So y is the force and m is the spring constant (size of force that stretches spring by 1cm) and b is 0.

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13. ## What affects the kinetic energy of a trolley?

Dependent Variables: I'll have several Dependent variables in this experiment to try and help keep it a fair test. The first one being that I'll keep all the other variables the same (e.g. Mass and Distance). I'll also make sure that I use all the same equipment (e.g. the same spring) and the last dependent variable will be that I will use the same surface through out the whole experiment. The reason for keeping all of these variables the same is to help keep the experiment fair, take for example if I changed the surface I did the experiment on

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14. ## Measuring spring constant using oscilations of a mass.

Diagram The diagrams of the experiment are on the following page Partial Diagram: Full Diagram: Variables Involved Independent variables * The extra mass that has been added on the spring (kg). Dependent Variables * Time for 20 oscillations measured in seconds Constant Variables * The height (m) from the table surface to the spring is going to remain constant throughout the experiment. * The effective mass, me (kg) of the spring that would be worked out would remain same through out the course of the experiment.

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15. ## Investigate the way in which extension depends on the tension for rubber.

Now the band is stretched it has the potential to do work. We know this as if we released the tension on it the elastic band would pull its self back to its original size and shape. The band must have elastic potential energy. Potential energy is stored in the band and is released when the tension on it is released. When discussing tension, we need to know what exactly tension is. Tension is the name given to a force which acts through a stretched material. So if the force exerted on a material is increased, i.e.

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16. ## The Oscillation Of A Spring.

Repeat the whole experiment three times for more accurate results and find the mean average for each. During this experiment, I will use three different springs, one for each set of results. They will all be identical, and will be made of the same material, and will be the same length. This is to ensure that the spring does not alter itself from being used in all three experiments, because if it did, the results would change. Preliminary Work: In my preliminary work I tested several things in order to amend and make more accurate the planning I have already done.

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17. ## Investigating the Vertical Oscillations of a Loaded Spring.

I will do this 3 times for each mass and average the results so as to reveal and eliminate any possible errors. I will use five different masses (100g, 200g, 300g, 400g, 500g,) so as to get a full spectrum of results and ensure that I check that elastic constant does not change with mass (it should not as it is the constant of that material). Once having recorded the masses and their corresponding time periods I shall work out the elastic constant of the material in two ways, by calculation and by graph.

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18. ## Investigate stretching using Hooke's Law.

When you pull an elastic material, it stretches - increases in length. At first, when you double the pull, you double the increase in length. As the pull increases, however, you reach a point where the material no longer returns to its original shape. This pull is the elastic limit of the material. Increasing the pull still more eventually makes the material break. The elastic limit is where the graph departs from a straight line. If we go past it, the spring won't go back to its original length. When we remove the force, we're left with a permanent extension.

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19. ## My aim in this experiment is to investigate how the compression of a spring affects the amount of kinetic energy transferred to the trolley that it is attached to.

Apparatus I will be using the following equipment in my investigation: * Trolley (with spring attached) * Ruler * Cardboard * Light Gate (connected to a computer) * Smooth surface * Calculator Method The trolley will be adjacent to a wall, allowing the spring to compress against it. The light gate, position with a clamp, will be fixed directly above the trolley slightly away from the wall. There will be an upright strip of cardboard attached to the near front of the trolley which will pass through the light gate after the compression of the spring.

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20. ## Investigation of the structure of a cantilever beam.

The weights will be added from 100g till it becomes 1 kg, and every time we add 100g we must measure the deflection of the ruler. This can be done by measuring the initial position of the ruler and measure the deflection from the initial position to the bent position of the ruler with a ruler, to give the bent or deflected height of the ruler. As the weights are added to the ruler the side of the ruler where the weights are hung is under tension and the other side is in compression.

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21. ## Investigation based on Hooke's law.

Elasticity can also be shown in this simple diagram: The Molecular Level Description. Before. After. Combinations of springs. Hypothesis. 1) I think that the stretch of the two springs in series will be double the stretch of a single spring. 2) I think that the stretch of the two springs in parallel will be half the stretch of a single spring. Therefore if x were to be the single spring: 1) The springs in parallel would be 1/2 x 2)

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22. ## What is the spring constant?

After each weight has been added to the spring, a pencil mark will be made on the label. When the 12th weight has been added and the pencil mark made, the weights will be removed and placed in the order in which they were added. The label will now be removed and the compression measured and recorded to the nearest half millimetre. A new one will be put on and the process repeated twice so three sets of results are obtained. To try and reduce the error in the measurements, 3 sets of readings are taken, and the average taken.

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23. ## Find out about the energy changes in a tethered cart.

Therefore I will not change the angle of elevation of the ramp from the bench (which includes the height the end of the ramp is from the bench), the same spring and cart will be used throughout the experiment and the string will be tied on to the clamp, spring and cart with no adjustments for the whole experiment. After watching a preliminary experiment I decided on the ranges of distances that I would pull back the cart. I am going to take seven different values for this because having more points on graph makes it more valid as the best-fit line can have a more definite position.

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24. ## Physics - The aim of this practical investigation was to obtain a value for the spring constant k for a decided system of springs.

Diagram for Hooke's Law experiment Method Set up the apparatus as shown above, I will be using three springs in series in my experiment. Ensure that the ruler is vertical, making sure not to knock or move the apparatus at all after it has been set up. For safety place a large mass on the clamp stand to prevent it from falling over. Various other safety considerations must be taken such as limiting the size of masses used, wearing safety goggles in case of flying springs and keeping feet well away from possible falling masses.

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25. ## Investigation to show how Elastic Bands Behave Under Load.

The elastic band will regain its initial shape and it behaves elastically. The thinner band will also have a longer extension because the molecules are less intertwined and so the band isn't as strong, when weight is applied the band will stretch further than a thicker rubber. In the thicker rubber band the molecules are more intertwined therefore the band will become stronger so the band will not stretch as far. In the shorter rubber band the molecules are much smaller and are more intertwined, this causes the band not to stretch, as far so it will have a smaller extension.

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