#### The purpose of this laboratory investigation is to verify the validity of the Lens Equation which states that 1/di + 1/do = 1/f.

Lab: Applying the Lens Equation Daniela Perdomo Lab Partner: Stephanie Landers Date: 21 November 2002 Place: Graded School - São Paulo, Brazil Time: 8:10 h - 9:35 h Purpose/Introduction: The purpose of this laboratory investigation is to verify the validity of the Lens Equation which states that 1/di + 1/do = 1/f, where di is the distance from the image to the lens, do is the distance from the object to the lens, and f is the focal length. Hypothesis: The laboratory investigators hypothesized that the data obtained in the procedure of this experiment would be consistent with the Lens Equation. Though different methods of obtaining focal lengths (f) will be used throughout the lab, the obtained f's should still be equal. Materials: * 2 double convex lenses * 1 candle * 1 box of matches * 1 meter stick * 1 lens holder * 1 cardholder * 1 candleholder * 1 blank card Diagram: Procedure: The first lens used in this investigation was a double convex lens, which indicates that light should converge when shone through it. The first way used to discover its focal length was by using sunlight. A cardholder, with a card in it, was placed on the meter stick and the lens holder, with the convex lens in it, placed in front of it (i.e. closer to where the sunlight was coming from). The lab investigators then moved the lens until the image on the card was focused enough

• Word count: 1671
• Level: AS and A Level
• Subject: Science

#### How has the Invention of Contact Lenses affected people's Sight?

Manon Mollard MP5a 14.12.04 Biology: The Impact of Man's Inventiveness on the Human Body. How has the Invention of Contact Lenses affected people's Sight? Introduction People with sight troubles have had the possibility of wearing glasses for a really long time, but the new technology made available contact lenses. In this essay, I am going to look at the different contact lenses types that exist, at who invented them and when, for which vision problems they are solution, at how to take care of them, at how common they are in our society and finally, I will write about my own opinion. What contact lenses are According to the Macmillan Dictionary (2002), contact lens may be defined as "a plastic lens that you wear in your eye to help you see more clearly". A very wide variety of contact lenses are available in today's society, including hard and soft (even if soft is by far more common now), disposable and extended wear; this makes it easy for each person to chose the appropriate type of contact lens for her. The main types of contact lenses are listed below: * Soft lenses: As these lenses are soft, they are made of a large percentage of water, and this allows oxygen to pass through the lens and reach the cornea. They are also more comfortable and easier to adapt to. * Rigid-gas

• Word count: 2286
• Level: AS and A Level
• Subject: Science

#### To Determine the Focal Length of a Convex Lens.

To Determine the Focal Length of a Convex Lens. Aim: To determine the relationship between the power of the vocal lens, object and the image distance from the lens. Apparatus: Bulb Projector Convex lens Lens holder Screen Optical Bench 12V power supply Diagram: Method: * Set up the apparatus as shown in diagram. * Put the focal lens at the first distance shown on the results. Also put the object at the 0 point of the optical bench. * Switch the 12V bulb and move the projector until a clear picture of the object is visible. * Record the results on the results table of the distance from the lens to the projector * Keep on moving the object to the 6 points shown on the results table and record the distances when object is visible for each measurement * I will do the experiment twice for each measurement to ensure that the results are accurate Safety: Making sure that all bags are put under tables will make this experiment safe. Also the work surface will be cleared of all books and other mess, which will mean that the table will be empty and easier to work on. The bulb will be hot so I will make sure that no one touches it or looks directly at it because it will also be very bright. Theory: The distances from the lens to the screen (U) as well as measuring the distance from the lens to the projector (V) will make me think of a formula. I have obtained a

• Word count: 646
• Level: AS and A Level
• Subject: Science

#### Setting up a Light Microscope.

Setting up a Light Microscope Aim: To set up a Light Microscope Microscopes came into existence in 1670. It was a man called Antoni Van Leeuwenhoek who came up with this innovative idea of inventing a Microscope. Soon his invention was very popular. Scientists everywhere started to utilize similar microscopes. Microscopes have been an asset to the scientific industry. We nowadays use microscopes to things in a greater detailed picture. The naked eye cannot see an onion cell, to observe the onion cell we need to use a Light Microscope. When using a Light Microscope we can adjust the magnification to what we desire. A light microscope is an excellent piece of equipment to use when distinguishing between an animal and plant cell. There are many types of microscopes. Two common microscopes are the Light Microscope and the Electron Microscope. Electron Microscopes are those that are used in big science laboratories. They can magnify up to a huge 500,000x. Whereas, a standard light microscope can only magnify upto 1000x. There is also a massive price difference between the two microscopes. An Electron Microscope can cost up £2.5 Million and a good light microscope will only cost about £50. Method You have to be very careful when using a light microscope. Follow these i9nstructions to setup and use the microscope properly. * First of all place the microscope in the

• Word count: 724
• Level: AS and A Level
• Subject: Science

#### The advantages and limitations of electron microscopy.

The advantages and limitations of electron microscopy There are two main branches of microscopy that are pertinent to cell biology. These branches arise from the two types of microscope; the light microscope and the electron microscope. The basic principles of light microscopy have been known since circa 17th century, however improvements in lens manufacture in circa 19th century allowed the use of microscopy to be much more practically available and useful. This is increased ability inspired rapid research into both the design of microscopes and the preparation of specimens. However, the light microscope can only magnify objects bigger than 0.2 micrometres; due to its limited resolving powers. This is because it utilises a beam of light. Relatively, light has a long wavelength, this means that when there are two small points close together there is too much refraction and wave front overlap, the eye then only sees one point. This can also be considered in terms of objects "crossing the path" of the wavelength. The smallest wavelength of visible light is 400nm, the diameter of mitochondria is 1000nm, and therefore mitochondria cross the path of the light wave. However ribosomes have a diameter of 22nm, and do not cross the path of the light wave and are therefore not seen by the light microscope. As biologists came to realise these limitations they understood that the

• Ranking:
• Word count: 1308
• Level: AS and A Level
• Subject: Science

#### Given a Tube Containing a Lens, Calculate The Focal Length of The Lens and Where The Lens Lies Within The Tube.

Given a Tube Containing a Lens, Calculate The Focal Length of The Lens and Where The Lens Lies Within The Tube. Plan I plan to set up the apparatus as shown below and change 'b'. To then make the image focus, I will have to change 'c'. When the image is focused, I will measure 'c' and also the magnification of the image. Using this information I will then be able to calculate 'a'. Hypothesis I predict that using the equations stated in the justification, after measuring values for 'c' and 'm'. I will be able to plot them on the graph of 'c' against 'm' Using the equation c = fm + [f - a]. I believe that if all the equations work, a straight line will be obtained. Safety After considering all aspects of this experiment, I have come to the conclusion that there are no significant safety issues. If normal levels of care are exercised, then there should be no risks involved. Variables that alter * b and c, (from diagram) * Magnification Variables to control * a (from diagram) * Ambient light * Part of object for which magnification is measured each time. * Place b is measured from and to Apparatus list * 0.15m tube * Lens * Object * 12V Power pack * Light source (lamp) white light average wavelength 550Nm * White screen * 2 x 1m rulers (0.0001m increments) * 0.15m ruler (0.0001m increments) * Stand and clamp * Spirit level Method

• Word count: 2136
• Level: AS and A Level
• Subject: Science

#### Identification of purpose of physics.

Greenwich Royal Observatory Identification of purpose of physics From my visit to the Greenwich Royal Observatory, the first aspect of physics that I will be showing an understanding for is the time keeping due to the earth's movements. Time keeping is on of the most important and what make Greenwich the most famous place for the "creation" of measuring time efficiently. Everyone needs the time and that's why so many years were put into inventing the "perfect" clock. The physics behind the clock is to get an exact measurement of 1 second. This has been achieved by pendulums, weights and now by computer. Time has been completely based on the earth's movement. Early on time was just measured by the light of day but then this all changed due to the stars. In the 1700's people started to measure the earths spin by using the starts. At night the looked up and pinpointed a star. The following nigh they would wait for that start to appear in the same place. The time between this was 24 hours. This was a great result due to the fact that there were 12 months in a year and this could easily let the time "integrate" with this number. However they shortly found out that seconds were being gained and lost due to the earth spinning round the sun. This means that they need some way in keeping the time correct after years. This is here the atomic watches came in. These

• Word count: 979
• Level: AS and A Level
• Subject: Science

#### Use of the material Zerodur in the KECK observatory telescope. The very low CTE makes ZERODUR ideal for use as part of the primary mirror. This means that over the temperature range that is possible that the telescope works in, (0-50C), the materi

Introduction The KECK observatory lies near the summit of Mauna Kea in Hawaii. There are two telescopes close to each other on the summit, KECK I and KECK II. These combine to form one of the largest optical telescopes in the world, second only to the Gran Telescopio Canarias (GTC) in the Canary Islands. For good reason, both the KECK observatory and GTC use the same material for their primary mirrors. The primary mirrors of the telescopes are the largest mirrors of the operation, and are designed to gather as much light as possible. The bigger the primary mirror, the more light the telescope can gather, and hence the 'further' into the solar system the telescope can see. With the need to see more and more of space, larger and larger telescopes are being built. However, making a mirror with a diameter of 10 metres of more out of a single sheet of a reflective substance gives a very large problem; the mirror must be very thick in order to hold its shape. When KECK I was being designed, the engineers came up with an ingenious solution, which involved splitting up the mirror into many hexagonal sections, which, when attached together, would act as a single mirror. This meant that the primary mirror would be made from smaller sections, allowing easier maintenance, installation and construction. The mirror is made of 36 hexagonal sections, and forms a slight curve, as shown in

• Word count: 2300
• Level: AS and A Level
• Subject: Science

#### Telescopes - research into types and properties of telescopes

Telescopes are instruments that magnify distant objects. Astronomers use telescopes to study the planets, stars, and other floating bodies. In most telescopes a lens or mirror is used to form an image of an object. The image may be viewed through an eyepiece or recorded on photographic film or by electronic devices. Telescopes produce images of objects too far away to be seen by the unaided human eye. The Dutch optician Hans Lippershey designed the first telescope in 1608, when he mounted two glass lenses in a narrow tube. Within a year the Italian astronomer Galileo built a similar device and became the first person to use a telescope to study the sky. Optical Telescopes Optical Telescopes use a lens or mirror to collect and focus light waves. There are three main types of optical telescopes. Refracting telescope Refracting telescopes also known as refractors have a large lens called an objective lens at one end of a long, narrow tube. The lens is convex on both sides so that the middle of the lens is thicker than the edges. The glass slows the light rays as they pass through the lens. (A wave is slowed most in the middle of the lens where the glass is thickest). The lens therefore causes the entire crest of the wave to arrive at the focus at the same time. Refractors with a magnifying eyepiece invert the image so that it appears upside down as astronomical observations

• Word count: 1531
• Level: AS and A Level
• Subject: Science

#### The Principles and Limitations of Scanning and Transmission Electron Microscopes

The Principles and Limitations of Scanning and Transmission Electron Microscopes Electron microscopes were first developed due to the limitations of light microscopes (3). The smallest object that can be viewed by any microscope is half the wavelength of light used, and objects smaller than this cannot be seen. This is because the object has to be large enough to interfere with the waves radiation. Light has a wavelength between 400-700nm, so the smallest object that can be viewed using visible light is 200nm(3). By the early 1930's all the possible scientific progress on understanding the inner parts of cells had been made, and scientists wanted to see more detail. Max Knoll and Ernst Ruska then developed the electron microscopes in 1931 (7). Electron microscopes use the same principles as light microscopes, but a beam of electrons is used instead of a beam of light. Electron beams have a wavelength of about 0.005nm. This short wavelength means much smaller objects can be seen (3). The resolution of a microscope is its ability to distinguish between two objects that are very close together. Magnification shows the objects as one larger image. The shorter the wavelength, the better the resolution. Therefore the resolution of an electron microscope is better than a light microscope. The magnification is also better. Magnifications of x250 000 can be obtained with an electron

• Word count: 1410
• Level: AS and A Level
• Subject: Science