#### Study the interference of light using Helium - Neon Diode Laser.

AIM TO STUDY THE INTERFERENCE OF LIGHT BY USING HELIUM -DIODE LASER COHERENT SOURCES As we see later, light waves from a sodium lamp, for example, are due to energy changes in the sodium atoms. The emitted waves occur in bursts lasting about second. The light waves produced by the different atoms are out of phase with each other, as they are omitted randomly and rapidly. We call such sources of light waves as these atoms incoherent sources on account of the continual change of phase. Two sodium lamps X and Y both emit light waves of the same colour or wavelength. But owing to the random emission of light waves from their atoms, their resultant light waves are constantly out of phase. So X and Y are incoherent sources. Coherent sources are those which emit light waves of the same wavelength or frequency which are always in phase with each other or have a constant phase difference. As we now show, two coherent sources can together produce the phenomenon of interference. INTERFERENCE OF LIGHT WAVES, CONSTRUCTIVE INTERFERENCE Suppose two sources of light, A, B have exactly the same wavelength and amplitude of vibration, and that their vibration are always in phase with each other, fig.1. The two sources A and B are therefore coherent sources. fig.1 Their combined effect at a point is obtained by adding algebraically the displacements at the point due to the sources

#### I am doing an investigation in to how much a metre rule bends when one end is clamped to a table and a varied load is attached to the other end that hangs off the table, thus bending the rule.

Physics Sc1 The Plan: Simple procedure: I am doing an investigation in to how much a metre rule bends when one end is clamped to a table and a varied load is attached to the other end that hangs off the table, thus bending the rule. I shall take relevant readings that I shall repeat three times and record the results in a table. Hypothesis: I hypothesise that the greater the load attached to the metre rule, the more the metre rule will be inclined to bend. There are two reasons for this. The first is because 'the extension is directly proportional to the stretching force.' This is Hooke's Law but cannot only be applied to springs, but also to metal wires, girders in bridges, but more importantly anything where the extension will be affected by the load. To see if my prediction is correct I will experiment, and obtain results using Hooke's Law. He found that the extension is proportional to the downward force acting on the spring. The formula that represents that is:. This is where F = force in Newton's, k = spring constant and x = extension in metres. I also believe that the amount that my metre rule will bend shall be quantitative. By this I mean that if the load doubles, so will the extension. I believe that if I put on three times the load, I will get three times the extension (and so on until eventually the metre rule cannot hold any more weights and snaps.) This

#### The Stiffness Of Springs

The Stiffness Of Springs Task The spring constant is a measure of the stiffness of an elastic system. How is the stiffness of a single spring related to the stiffness of springs in series and parallel? Plan an experiment that will enable you to make a comparison of the stiffness for identical springs in series and parallel from your results. Plan The task of this experiment is to determine the relationship between the stiffness of springs in series an in parallel. The stiffness of a spring can be shown as: F = kx Where F is the force on a spring, x is the extension of the spring and k is the spring constant or the spring's stiffness. This means that the force on a spring is proportional to the extension with k being the constant. Therefore as more force is put onto a spring the more it will extend. By using this simple formula we can find the spring constant. k = F/x By dividing the force by the spring extension we can find k. Both the force and the spring extension are easily measurable. We can show the relationship between the force and the extension in a graph. x . F The graph shows that as the force gets bigger the extension does. The gradient of the line is the spring constant. It is a straight line, as the spring constant does not change up to a certain point. There is a point when a certain force will create a very large extension. This

#### What affects the voltage output of a solar panel?

What affects the voltage output of a solar panel? Planning Aim The aim of the investigation is to find out how the distance between a light point source and a photovoltaic cell affects the output potential difference. Hypothesis I predict that the further the distance, the smaller the output potential distance Inverse square law for light intensity (Taken from the website - http://hyperphysics.phy-astr.gsu.edu/hbase/vision/isql.html#c1) "Inverse square law for light intensity against distance: As the distance between an observer and a light source increases, the observable brightness decreases with d-2. Light spreads out over an increasing area of space to decrease apparent brightness. (Figure 1.1) Figure 1.1 (http://www.astrosociety.org/education/publications/tnl/32/images/fig5.gif) Because, Pin is proportional to area-1 and area is proportional to distance2, therefore Pin is proportional to distance-2 (figure 1.2). This supports my prediction that the output potential difference will be much smaller when the distance between the point source and the PV cell increases. Of course, my hypothesis assumes 100% efficiency and no influence from background light and other factors that may affect the experiment in anyway. .2 Prediction of outcome (Pin ? distance-2) Apparatus list The list of apparatus to be used is: Ray box Used as the point source to emit light

#### An investigation into the stretching of materials

Kate Graham 10 Tees Moor An investigation into the stretching of materials PLANNING I am examining the stretching of materials. I decided that research on Hooke's law, (The law named after Robert Hooke who formulated the law governing elasticity), and more particularly the way elastic bands reacted to stress would help me to do this, so I found as much material as I could, relevant to my investigation, that would help me. This material is at the back of this document. Elasticity is defined as the property or substance in a material that causes the material to resume its previous size and shape after having been stretched (or compressed) by a force, and this is what I have decided to investigate. According to my research below, Hooke's law states that a force applied to an object creates a tension within that object and the stress can cause the material to 'deform'. Stress is directly proportional to strain, defined as the quantity that expresses the amount of deformation. The strain is therefore linked to the tension created. Hooke's law is defined as a law expressing the proportionality of strain to the stress causing it. Apparatus The appropriate pieces of equipment I have chosen to use in my experiment are; · Elastic bands of three different lengths, 2cm, 4cm and 6cm, · A clamp and stand, · A metre ruler, · Six weights each weighing 1 Newton.

#### Dark Matter

Dark Matter Introduction Throughout the years, scientists have been looking for the missing mass of the universe; it has yet remained an unsolved mystery. Using different methods, scientists have tried to determine the mass of the universe and surprisingly found a discrepancy suggesting that ninety percent of the mass of the universe is nowhere to be found. Then here comes the term "dark matter", referring to this unfound matter of the universe. It is called dark because it gives off no light and matter because it has to have some mass to be able to explain the effects that they produce. There have been different perspectives about dark matter. Some scientists think that dark matter is in the form of black holes, very massive objects floating around in the universe still unseen. While there are some that believe that dark matter are subatomic particles that never or seldom interact with matter. So how did the matter over dark matter come about? Before we will be able to tackle the issue of the theory of dark matter, when, why, and how it existed, let us first study the evolution of the different studies of the universe. Ptolemy and the Solar System Long time ago, scientists believed that the sun revolved around the earth, they all agreed with the scientist Ptolemy's explanation that the earth was like a stationary globe where other seven planets revolved around it.

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

MEASURING SPRING CONSTANT USING OSCILATIONS OF A MASS. Aim The aim of this experiment is to use oscillations of a mass on a spring to the find the spring constant, k and the effective mass of the spring. The reason to carry out this experiment is to find the value of the effective mass, me and to see if it is small enough to be ignored as some teachers think or not. Apparatus * Spring * Weights * Stopwatch * Retord Stand * Clamp * Table Apparatus Specification Apparatus Range Of Measurement Maximum Measurement Minimum Measurement Weights 0.100Kg - 0.600Kg 0.600Kg 0.100Kg Stopwatch 0.01 sec - 356400.00 sec 356400.00 sec 0.01 sec Method The apparatus will be set up as shown in the diagram. The Retord stand and the clamp are going to be used to hang the spring a certain height above the surface of the table. The masses are going to be kept nearby along with the stopwatch to measure the oscillations. Initially the time will be recorded for 0.100Kg. The spring would be given a reasonable vertical displacement for which the time would be recorded. Which is the time for 20 oscillations. The time recorded would be for 20 oscillations. This experiment is then repeated for the same weight three times and then for the rest of the weights up to 0.600Kg. The reason to carry out the experiment three different times for the same mass is to get a reasonable

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

PH 6 - Physics Coursework Aim The aim of this practical investigation was to obtain a value for the spring constant k for a decided system of springs. Summary A value for k for a chosen spring system was deduced from two separate experiments. The some possible methods were : - .) Hooke's Law - using a set of known masses to stretch a spring system. Deriving k from a Force-Extension graph. 2.) Period of Oscillation of a Mass (SHM) - on a spring system. Using a set of known masses, showing how the period varies with suspended mass. Deriving k from a suitable graph. 3.) Resonance of the spring system - The two k values were then compared and analysed to see which method gives the better value. The two values were 8.09Nm-1 and 7.57 Nm-1. Hooke's Law Theory Using the equation F = kx where F = the force exerted on the spring by the mass in Newtons (N) k = the spring constant in Newtons per millimeter (Nmm-1) and, x = the extension observed in millimeters (mm) I will plot an F-x graph from which I will obtain a gradient and y-intercept which I can use to compare the above equation to the straight line equation y = mx + c where mx = gradient and, c = y-intercept So, y = mx + c F = k + x Therefore, the gradient of my F-x graph, which should pass through the origin, will equate to the k value of my spring system. Diagram for Hooke's Law experiment

#### The Anglers Problem

The Anglers Problem Aim To use rubber bands to produce an accurate and reliable spring balance to weigh fish caught by an Angler. We have to consider how reliable and sensitive the gauge will be. Prediction I predict that the greater the weight applied to the band, the further it will stretch. This is due to extension being proportional to load, and so if the load increases so does the extension and so does the stretching distance. I believe that the best device would produce results to form a graph similar to the one below (line of best fit shown in red). I predict that the two bands in series will be the most sensitive device, due to its length. It will also be more stretchy (blue line). However its elastic limit will not be that high. The 2 bands in parallel will not be as sensitive but it will have a high elastic limit (green line). I believe that the 2 parallel connected to the one band will be a good device. It will be sensitive (due to its length) and it could cope with a heavy load due to the thickness of the top half. The two bands in parallel connected to the two bands in parallel will be both sensitive and strong. This would make the best device. Hypothesis Hookes Law states that if you apply force (f) to a spring, the spring will stretch by some length (x). Doubled force means double the stretch. This is known as a mathematically direct relationship. Line

#### An investigation into the effects of a force applied to a spring and the time for it to complete a set number of oscillations

An investigation into the effects of a force applied to a spring and the time for it to complete a set number of oscillations Plan Intro: I am going to investigate the effects of a force applied to a spring and its relationship to the time it takes for the spring to complete a set number of oscillations, when the displacement is constant. While conducting this investigation, I will always bear in mind, that I would like my results to be as accurate and reliable as possible. I have also previously conducted an investigation into the elasticity of a spring, which showed me that the force applied to a spring and its extension as a result of the force applied is directly proportional or constant. Could this imply that the frequency or the oscillations per second have a constant relationship to the force applied also? Safety Safety is paramount in all scientific investigations and this will be no exception. All masses and weights will be handled with care. Masses will not exceed the spring's maximum tolerance so there is no danger of the springs wire breaking. Food will not be consumed in the laboratory nor will drinks be drunk. People will not run in the laboratory. Safety spectacles will be worn so that if, by some unforeseen reason, the spring were to break, eyes will be kept safe. Fair test This will be a fair test by all other variables, within my control, being