101 results found

#### What is an atomic orbital?

ATOMIC ORBITALS What is an atomic orbital? Orbitals and orbits When the a planet moves around the sun, you can plot a definite path for it which is called an orbit. A simple view of the atom looks similar and you may have pictured the electrons as orbiting around the nucleus. The truth is different, and electrons in fact inhabit regions of space known as orbitals. Orbits and orbitals sound similar, but they have quite different meanings. It is essential that you understand the difference between them. The impossibility of drawing orbits for electrons To plot a path for something you need to know exactly where the object is and be able to work out exactly where it's going to be an instant later. You can't do this for electrons. The Heisenberg Uncertainty Principle (not required at A'level) says - loosely - that you can't know with certainty both where an electron is and where it's going next. That makes it impossible to plot an orbit for an electron around a nucleus. Is this a big problem? No. If something is impossible, you have to accept it and find a way around it. Hydrogen's electron - the 1s orbital Suppose you had a single hydrogen atom and at a particular instant plotted the position of the one electron. Soon afterwards, you do the same thing, and find that it is in a new position. You have no idea how it got from the first place to the second. You keep on

• Word count: 6636
• Level: AS and A Level
• Subject: Science

#### My experiments focus is to obtain an accurate measurement for a specific lenss power.

Quality of Measurement Coursework: 'The power of a lens' Andrew Ensten Aim My experiments' focus is to obtain an accurate measurement for a specific lens's power. This will be achieved by focusing on the lens equation: /v (curvature of wavefront after lens) = 1/u (curvature of wavefront before lens) + 1/f (power of the lens/curvature added by lens). By performing an experiment with a source of light, a lens, and a screen, I will obtain several 1/u and 1/v values. When these values are plotted on a 1/v against 1/u graph, they will hopefully give me an accurate estimation of the power of the lens by looking at the axes intercepts. Equipment: * Power pack: For each experiment I kept the output setting to 9 Volts to control the power being delivered to the filament lamp (as power = current x voltage). Power is proportional to intensity and so a brighter/darker output could result in a different range where the created image is in focus. * 2x Wires: These took the electric current from the power pack to the light source I was using. * Filament lamp: I chose a filament lamp over other sources of light as it is easy to tell when its' image is formed. This is because the filament is a very definable object. I used it for my first, third and fourth experiments. With a constant voltage output; the intensity of light was relatively constant. * Light Emitting Diode: I

• Word count: 5969
• Level: AS and A Level
• Subject: Science

#### In this experiment I will be investigating the efficiency of a motor. I hope to calculate a range of results when the motor lifts varying weights.

AS Level Experiment Hermanjit Virk 12WSI Electric Motor Efficiency Coursework Plan Aim: In this experiment I will be investigating the efficiency of a motor. I hope to calculate a range of results when the motor lifts varying weights. Apparatus: Ammeter Circuit Leads Crocodile Clips G Clamp Motor Power Supply Ruler/ Scissors/ Tape Stop Watch Variable Resistor Voltmeter Weights Wire Diagram: Safety: In this experiment it is important to consider the safety aspects when carrying out this practical task; I will make sure of the following things before starting the experiment: * The circuit has been connected correctly according to the circuit diagram (Previous page) * Make sure that the connected leads are all working in order and are not tangled * Check that the motor is working correctly * The Power supply is working, and the voltage is not exceeding the limit * Check the circuit before starting and be standing during the experiment * A Mat should be placed on the floor as weights will land on to the ground Keeping the same Changing Current Length of string /Height Temperature Voltage Motor Weight Variables: Theory: Efficiency is often expressed as a percentage. What efficiency shows us is the power wasted in the experiment, not all the power is used efficiently as it is wasted when the power is being transferred. The power

• Word count: 4317
• Level: AS and A Level
• Subject: Science

#### Relationship Between U and V For a Convex Lens

SC 1 Relationship between u and v for a convex lens Prediction I think that when the length of 'u' increases (object distance), the length 'v' will decrease. (image distance.) Only when the object is greater than the focal length of the lens, is a real image is produced. If the object distance is nearer the focal length than a virtual image is produced. The virtual image has a negative distance from the lens, which means it can't be focused onto the screen. When plotting my results on graph, I will expect them to produce a curved line for u over v, producing a reciprocal graph. However a straight line when plotting 1/u over 1/v. Scientific Ideas This formulae for the focal length of an object: /focal length = 1/object distance + 1/image distance The following formulas are rearranged from the one above. This will help me throught my experiment, and with my scientific ideas. u = object distance f = focal length v = image distance (20.0 cm) (15.0 cm) (60.0 cm) f = 1 / (1/u + 1/v) 15 = 1 / (1/20 + 1/60) (FOCAL LENGTH) f = (uv) / (u + v) 15 = (20*60) / (20 + 60) u = 1 / (1/f - 1/v) 20 = 1 / (0.06 - 0.016) (OBJECT DISTANCE) u = (vf) / (v-f) 20 = (60*15) / (60-15) v = 1 / (1/f - 1/u) 60 = 1 / (0.06 - 0.05) (IMAGE DISTANCE) v = (uf) / (u-f) 60 = (20*15) / (20-15) FOCAL LENGTH = 15 cm u (cm) v (cm) 0.00 - 30.00 20.00 60.00 30.00 30.00

• Word count: 4284
• Level: AS and A Level
• Subject: Science

#### Lenses experiment

Planning Hypothesis I hypothesise that moving the object further away from the focal point of a converging lens will decrease the magnification of the size of the image. Apparatus Method I will set up the apparatus as shown in the diagram above. To decide which lens I am to use I will find the focal lengths of different lenses and us the lens that gives the easiest focal length to work with, this will be found out in my preliminary experiment. In this experiment I will be trying to prove my hypothesis, to do that the results that I obtain have to help me find the magnifications of different lengths away from the focal length. The object will be put on the focal point for the first result then I will measure the diameter of the object, this should always be 2.0cm, and then I will measure the diameter of the image. I will record my results into a suitable table; all of my results must be to 1 decimal place apart from the results for the magnifications, which will be to 2 decimal places. I will obtain results every 2.0cm and take four results so that I can take an average result for the object distance (U), for the width of the image and the magnification. I will obtain results every 2.0cm because the image size drastically changes at the beginning when moving it away from the lens just a little bit and less so later on when got past 2F(twice the focal length), therefore

• Word count: 3668
• Level: AS and A Level
• Subject: Science

#### The eye.

The adult eyeball is about 2.5 cm in diameter. The eyeball is held in place by six extrinsic muscles, which allow the eye to be moved. The front surface of the eye is protected by the eyelids and the eyelashes. The reflex action of 'blinking' protects the surface of the eye. Under the eyelids is a thin transparent layer called the conjunctiva. This is kept moist by secretions from the lachrymal glands (tear glands) which lie above and to the outside of each eye. The fluid contains the enzyme lysozyme which kills bacteria. After passing over the conjunctiva, it drains from the eyes into the nasal cavity. The eyeball has a three layered structure. Structure of the eye Iris - regulates the amount of light entering through the pupil. Iris is a continuation of the choroid. Pigmented, colour of eye. WALL OF EYE IS COMPOSED OF THREE LAYERS: (a) Sclera Sclerotic - outer layer, tough protects and helps maintain shape of eye. White except at front where transparent - called cornea. (b) Choroid - middle layer, vascular, feeds retina cells. In humans, cells contain a black pigment melanin, which prevents light reflection in the eye. (c) Retina - inner layer, light sensitive cells - cones and rods. Fovea (yellow spot) in man only cones found here. Blind spot, retinal absent - where optic nerve leaves eye. Filled by jelly-like vitreous humour containing about 99% water,

• Word count: 3286
• Level: AS and A Level
• Subject: Science

#### Proving the lens formula.

Jack Webdale 02/05/2007 Page 1 Proving the lens formula Background information When light passes from air to a denser material it slows down. In a concave lens the light has to travel further through the middle then through the sides. This has the affect of pushing the waves back in the middle and forward around the edge therefore effectively adding curvature to the wave. A similar thing happens when passing through a concave lens but obviously vice-versa, taking away curvature of the wave. The curvature that the lens adds or takes away is the Power of the lens, measured in dioptres. P=1/f, P is the power of the lens and f is the focal length. The focal length of a lens is the distance from a lens to its focal point, which is where the image of a distant object is formed. The shorter the focal length the more powerful the lens. The following formula is what I am going to attempt to prove that it is valid. It is used to give the focal length, and hence where the image is focused. /v+1/u=1/f Where v is the distance from the lens to its focal point, u is the distance from the object to the lens and 1/f is the power of the lens. This follows from the above, the power shows how much curvature is added to the wave. As a wave moves further away from an object the curvature of it decreases. This formula may also help me with my progress, as I can use it to calculate the

• Word count: 2745
• Level: AS and A Level
• Subject: Science

#### To investigate the relationship between the distance between a lens and an object, and the distance a screen must be from the lens in order that it displays a focused image of that object on the screen.

Lenses "An investigation into the factors affecting a lens." Aim: To investigate the relationship between the distance between a lens and an object, and the distance a screen must be from the lens in order that it displays a focused image of that object on the screen. Background knowledge: In order to plan and my investigation, I am going to research the different types of lenses and the factors affecting them, and their uses. I hope that this will help me to plan and carry out a more successful investigation, and also help me formulate a hypothesis and understand my results better. Lenses are optical devices that affect the passage of light through them by refraction. They can be made from almost any transparent materials, but the most common is glass. Lenses are used extensively in optical instruments such as cameras, telescopes and all sorts of projectors. There are two main types of lens, convex (converging), and concave (diverging). Convex lenses are thicker in the centre, thinning out towards the edges, while concave lenses have thick edges and thin centres. A concave lens will refract light inwards, thus creating a smaller image while a convex lens will do the opposite, creating a larger image. All lenses have an optical centre, where light can pass without being refracted and the principal axis of the lens passes though this point. At this point on the lens,

• Word count: 2693
• Level: AS and A Level
• Subject: Science

#### Does the focal length of a lens depend on the colour of light used?

Physics coursework PSA3 experiment Does the focal length of a lens depend on the colour of light used? Aim The aim is to investigate the Focal lengths of light in the visible spectrum. Introduction I intend on using light with as much difference in wavelength as possible so that I can compare my results with more ease and so that errors in my experiment do not lead to overlapping results that have no distinct difference in them. However as I am restricted to a school laboratory I shall be using light on the part of the electromagnetic spectrum visible to the human eye. This is because filters for red and blue light can be found and used easily and have a large enough wavelength difference (red light with a wavelength of around 700nm whilst blue light is nearly 400nm) as they are on opposite parts of the visible spectrum to each other. Before I started the experiment I was given the lens I was going to use in the experiment so that I could work out the rough focal length of the lens. This meant that I could work out the distances I will I was going very useful because the equation I was going to use was 1/U + 1/V = 1/F My hypothesis is that light with shorter wavelengths will have shorter focal points. Throughout my coursework U will stand for ...... and V will stand for.......... Apparatus ) Ray box (12V) 2) Power supply (able to supply12V) 3) Object slide 4)

• Word count: 2626
• Level: AS and A Level
• Subject: Science

#### History of the Microscope

The Microscope Introduction History of the Microscope: From ancient times, man has wanted to see things far smaller than could be perceived with the naked eye. This led to the construction, in the 16th century, of a magnifier composed of a single convex lens, and this, in turn, led to the eventual development of the microscope. Perhaps the most famous early pioneers in the history of the microscope are Digges of England and Hans and Zcharias Janssen of Holland. But it was Antony van Leeuwenhoek who became the first man to make and use a real microscope. Leeuwenhoek ground and polished a small glass ball into a lens with a magnification of 270X, and used this lens to make the world's first practical microscope. Because it had only one lens, Leeuwenhoek's microscope is now referred to as a single-lens microscope. Its convex glass lens was attached to a metal holder and was focused using screws. After his historic invention, Leeuwenhoek continued to devote himself to studies base on the microscope. His discoveries included bacteria, bell animalcules and spermatozoa. Leeuwenhoek actually constructed a total of 400 microscopes during his prolific lifetime. The magnification ratio of a single-lens microscope like the one invented by Leeuwenhoek is calculated in the same way as calculations are made for a simple magnifying glass. 250mm accepted to be the distance of most

• Word count: 2340
• Level: AS and A Level
• Subject: Science