Physics of water waves.
All waves possess the properties of reflection, refraction, diffraction and interference. These phenomena's were observed with the use of a ripple tank. A ripple tank consists of a large rectangular tray with a transparent bottom. Water is placed in this tan to a depth of approximately one centimeter. A light source is then placed above the tray of water. When the water is disturbed it can be seen on a white surface positioned under the tray. The first phenomenon observed was reflection. It was found that water waves also follow the law of reflection. As straight waves strike a hard straight surface they are reflected at an angle equal to the angle of incidence. After reflection the wave has the same speed, frequency and wavelength as it did prior to the collision. This is similar to the reflection of circular waves off a straight barrier. The reflected waves are also circular, however they have a centre point that is position behind the barrier. This point is known as the "image" of the source. Reflection of a parabolic or concave barrier can be closely compared to that of light waves off a concave mirror. If the incident wave was straight, the reflected waves are curved, and they converge at a fixed focal point. After passing through the focus, the radius of the curves increase. The opposite is so when circular waves strike a concave barrier. The reflected waves are
What causes feedback in a guitar or microphone?
What causes feedback in a guitar or microphone? Just for the record, feedback is actually the mechanism used to control almost every electronic device manufactured. Stability is a critical issue for all of these feedback control systems, and the gain, or level of amplification, used is a critical element in their design. When musicians talk about feedback, however, the connotation is negative because it is the term they use to describe the shreek that results when the gain is too high on the output of an amplified instrument or microphone. There are several potential mechanisms by which feedback can occur when sound is amplified. Let's deal first with the simple case of a microphone and an amplified speaker. (See the figure, but ignore the guitar for now.) Feedback occurs when a "loop" between an input and output is closed. In this scenario, the microphone serves as the input and the amplified speaker provides the output. In our example, the loop between the input and output closes when the sound radiated from the amplified speaker reaches the microphone and is subsequently amplified again. In effect, the cat is chasing its tail. (See the dashed red line connecting the loudspeaker to the microphone through acoustic feedback in the figure.) Gain is an important factor in this instance; it also explains why equalizers are frequently employed to control acoustic feedback. The
Do mobile phones adversly affect our health? - Case study
-------------Contents----------------------------------------------------------------------------- Pg.2 ------------------------------------ Introduction, Scientific Theory Pg.3 ------------------------------------ Mobile Phones Are/Aren't Dangerous Pg.4 ------------------------------------ Comparison, Conclusion, Bibliography Pg.5 ------------------------------------ Bibliography continued -------------Introduction------------------------------------------------------------------------ I am doing a case study for physics with the hypothesis "Using a mobile phone affects our health negatively". I have begun by looking at different websites for the facts. For example The Times article says that "The number of mobiles in Britain has doubled to 50 million since the first government-sponsored report in 2000" and the International Communications Union tells us that "About half of the world's population has a mobile phone today with mobile phone ownership worldwide topping 3.3 billion at the end of 2007". This is confirmed below. These are just a few figures that explain how serious this hypothesis is. If it does affect your health negatively, then 3.3 billion people could be at risk. I have also stated my own opinion in a conclusion and Amount of Mobile Phones worldwide - Source: IC Insights -------------Scientific
What Is Fibre Optics
WHAT IS FIBRE OPTICS? To put it simply, fibre optics is a technology whereby a signal like video, data or voice, is concentrated on a light beam and sent down a glass tube over large distances, with very little distortion and loss. The principles of fibre optics are simple and easy to understand. All of us have seen the "broken straw" effect in a glass of water. When light travels from air to a denser medium, like glass for example, the light slows down by a factor equal to the optical index of the material and this slow down in speed results in bending of the light. As shown in the example when we see an object from underwater, the object is not in the actual position as we think because light bends travelling from water to air. When this angle of entry is increased, there would come a stage when the light is reflected back into the same medium, as shown in ray 3. This angle is called the angle of Total Reflection. Fibre Optics uses this simple principle for transmission. The core of the fibre optics cable, which is made of glass, has a higher index of refraction than the index of the cladding, which covers this core. So when light is injected into the glass core at the correct angle, it will reflect back from the surface and continue doing this in its forward direction of travel. In other words the light cannot "escape" from the fibre. COMPONENTS OF A FIBRE OPTICS
Experiment to Investigate which Factors Affect the Strength of an Electromagnet
Experiment to Investigate which Factors Affect the Strength of an Electromagnet Introduction An electromagnet is a magnet made of a solanoid with coils of wire around it. Aim To investigate which factors affect the strength of an electromagnet. Predictions I predict that the voltage, the amount of coils and the material of the solanoid can affect the strength of a magnet. I also predict that adding more coils increases strength. See domain theory. The Domain Theory The domain theory is that all the atoms point different ways in a piece of iron. When the piece of iron is magnetised all the atoms in the iron point to north. Variables The variables are the number of coils and the strength of the magnet. The number of coils I will change is in the independent variable and the strength of the magnet is the dependent variable. What I Intend to do I intend to investigate which factors affect the strength of an electromagnet. I intend to keep the voltage the same throughout the experiment I'm going to keep adding coils to the solanoid and find out how many paper clips it attracts. Apparatus Power Supply DC 0 - 13v demagnetising solanoid Connecting wires with plugs Crocodile clips Insulating wire (approximately 1m) Nail (soft iron) Heat proof mat Stand and clamp Paper clips Circuit Diagram Preliminary Experiment In the preliminary experiment I will check the
Resonance of a Wine Glass
Resonance of a Wine Glass Final Conclusions Reached The amount of water added to a glass affects its resonant frequency. As more water is added the frequency goes down. This is because the waves lose energy when they drag water molecules along with them around the glass.1 The more water in the glass, the bigger surface area is covered, and more molecules are exposed to the dragging effects of the waves of vibration throughout the glass. All four sets of results taken show a curved trend (although some more prominent than others). Similar shaped glasses appear to produce similar frequencies and my theory is that the energy taken by the water is proportional to the air left in the glass by a factor of k/x2 where could be any constant > 1 and x could be to any power >0. Originally I thought the consistency of the liquid in the glass would affect the sound it produced as I thought stronger intermolecular bonds would mean fewer molecules would be dragged around the glass and thus the frequency would not change as much as with water. However, after two tests, conclusive results showed I was wrong and this made no difference to the frequency of sound it produced. I came to no firm conclusion about the relationship between speed and frequency. I believe this is because there is more of a relationship between pressure and frequency. However, I couldn't test this at school as the
An investigation into the factors affecting the frequency of a standing wave
An investigation into the factors affecting the frequency of a standing wave Introduction There are several ways in which you can control the pitch (frequency) of a note produced by a string. A string with 2 fixed ends (called nodes) can produce different standing waves. The lowest frequency standing wave that can be produced has a wavelength ? where ? = 2l (l = length of string) This is related to the frequency ƒ of oscillation by the wave equation V = ƒ? Where V is the speed of transverse waves traveling along the string. You can therefore deduct that ƒ = v/? = v/2l ƒ therefore should be inversely proportional to the length of the string, i.e. the shorter the string, the higher the note. The frequency will also depend on the tension and the mass per unit length of the string, as they affect the speed of transverse waves traveling along the string. The greater the tension, the greater the speed, and the heavier the string, the lower the speed. This becomes important in this investigation because if the experiment is to be fair, then the two other factors affecting the frequency must be kept constant for the results to be accurate. I have decided to investigate the effect that altering the length of string along which the wave travels. From the above equations, I would expect the frequency to be inversely proportional to the length of string, as you would
Find the critical angle and refractive index for plastic using a graphical treatment for my results.
Investigating Refraction Aim: Find the critical angle and refractive index for plastic using a graphical treatment for my results. Introduction: The Refractive Index is how the much a material bends the light. In this experiment I will be looking at the how much the angle of incidence gets refracted and I will multiply my results by sine. I will plot a graph from my results and, using a line of best fit, I will calculate the size of the angle of incidence in order for the refracted angle to be equal to 900 (critical angle). I will then calculate the refractive index by using Sine I and Sine R. I will be looking at light going from glass to air (from a dense medium to a lighter one). Theory: Incident ray: Ray of light before refraction. Angle of refraction (R): Angle between refracted ray and normal at point of incidence. Angle of incidence (I): Angle between incidence ray and normal at point of incidence. Point of incidence: Point at which incident ray meets boundary and becomes refracted ray. Critical angle: The particular angle of incidence of a ray hitting a less dense medium, which results in it being refracted at 900 to the normal. Normal: A line at right angles to boundary through chosen points. There are two main laws of refraction of light: 1. The refracted ray lies in the same plane as the incident ray and normal at the point of incidence. 2. (Snell's law). The
Is Sunbathing Good?
Is Sunbathing Good For You? Tanushri Gukhool 10a Mr Terry Contents page Introduction.................................................................................pg2 Ultraviolet radiation.....................................................................pg2 The sun can be good for you.........................................................pg2 The sun can be bad for you..........................................................pg2 Sun beds..................................................................................pg3 How the Skin Tans.....................................................................pg3 UV and your health.....................................................................pg4 UV sessions..............................................................................pg4 Risks........................................................................................pg5 Who is most at risk?....................................................................pg6 Health benefits...........................................................................pg6 Tanning fakes............................................................................pg7 Tanning myths...........................................................................pg7 Conclusion................................................................................pg8
The Fundamentals of Radio Wave Propagation
The Fundamentals of Radio Wave Propagation How do radio waves get from one location to another? Why does a signal at generated at Point A, which is several thousand miles away, reach Point B without a complicated myriad of connecting wires? The answer, in three words, is radio wave propagation. Radio wave propagation theory is of particular importance to wireless communications, for, without a preliminary understanding of the physical nature of wave propagation it is impossible to ensure that communications can be established at all. * Transmission and Reception In a wireless environment radio frequencies are transmitted outward from a source, which is usually an antenna. Antennas provide the link between the grounded and free-space parts of a communications system. The transmitting antenna is charged with the task of transforming the electrical signal into electromagnetic radiant energy, the purpose of the receiving antennae is to accept the received radiated energy and efficiently convert it into an electrical signal for processing by the receiver. The portion of the electromagnetic spectrum that constitutes radio waves ranges from about 30 kHz to 300 GHz. (Fig. 1) Frequency Name Frequency Range Wavelength Low Frequency 0-300 kHz 30-1 km Medium Frequency (mf) 300-3000kHz 000-100m High Frequency (hf) 3-30 MHz 00-10m Very High Frequency (VHF) 30-300MHz 0-1m
