Report the best value you have for the focal length of each lens, including the concave lens. Report any relationships that you have observed during the analysis, and comment on the difference between positive and negative lenses.

Focal lengthcamera

where feq is the equivalent focal length of the lens combination, and f1 and f2 are the focal lengths of the two lenses that make the combination.

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Most optical instruments in common usage have one or more lenses in them. Whether it is a microscope, a telescope, or even a simple magnifying glass, the crucial element is a lens. The formation of images by lenses is one of the most important studies in the field of optics. In particular, in this experiment you will measure the focal length of both positive and negative lenses, and examine a combination of thin lenses.

Human eyesfocal length

From the lens combination using the concave lens, calculate the focal length of the concave (negative) lens. The algebraic value from the computation comes out negative, which is why it is called a negative lens. Why could you not measure the focal length of this concave lens by itself?

When you have completed this experimental activity, you should be able to: (1) define focal length; (2) differentiate between positive and negative lenses; (3) measure focal length for a single thin lens and for combinations of thin lenses; and (4) distinguish between a real image and a virtual image.

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When a beam of rays parallel to the principal axis of a lens impinges upon a converging lens, it is brought together at a point called the principal focus of the lens. The distance from the principal focus to the center of the lens is the focal length of the lens; the focal length is positive for a converging lens and negative for a diverging lens.

Using the lens equation (1), calculate the focal length of each lens or lens combination. Since you have found two focused positions for each lens, you should compute two values of focal length for each lens from the data. Average these two values. Compare, using percent difference, this average value with the value found by focusing a distant object. What do you notice about the object and image distances for the two positions of the same lens?

With the object and screen still fixed in the same positions, move the lens back and forth along the optical bench until another position is found where sharp image is formed on the screen. Record the object and image distances for this location, as well as the image size.

MetroLink Mechanic       Metro Transit seeks dedicated Electromechanics! If you’re someone who is interested in using your expertise to help others and improve our community, keep reading.   As an Electromechanic, you play an essential role in public safety and in keeping our transportation system running smoothly. Safe and reliable transportation starts with you! This is an opportunity to step out of the diesel garage and use your skills on clean electric trains. At Metro, you’ll provide specialized support and creative solutions for optimizing and maintaining Metro’s electric trains, while enjoying a rewarding career that has a positive, lasting impact upon the lives of your friends, family, neighbors and community!    Plus enjoy a full range of benefits, including medical/dental/vision coverage, paid time off, and so much more.   About Us   Metro Transit provides transportation throughout the Bi-State area to tens of thousands of riders every day. These passengers rely on the Metro Transit system, and more than 2,000 Metro professionals to keep their life and their communities moving forward. Our fleet of more than 600 Metro Transit trains, buses and vans are operated, maintained, and protected by bus/van operators, security personnel, customer service, mechanics, and engineers—a team ranging widely in age, experience and professional specialty, but are united by shared passion for the community they serve.   Why Work Here   Work for a company that strives to make a positive impact in the regionEarn competitive wageGym Discounts with Club Fitness and OneLife Fitness at Ballpark Village24 hour access to our 9 onsite gymsWellness program that provides free health screeningsDiscounted Cell Phone serviceFree MetroLink and MetroBus accessMedical, Dental, Vision coverageYour Birthday is a floating holidayUniform allowanceEmployee assistance programBi-State Development is an eligible employer the for Public Service Student Loan Forgiveness programTuition Reimbursement Available   Essential Outcomes   Duties include performing preventative and corrective maintenance through inspecting, servicing, calibrating, aligning, repairing, truing wheels, and diagnosis of all systems and subsystems of the LRV. Such systems and subsystems include such elements as the following: high and/or low voltage electrical and mechanical systems such as propulsion, printed circuit boards, amplifiers, logic gates, operation of thyristor, various applications of capacitors, relay switches and logic, static converter, motors, air brakes, compressors, HVAC, trucks, wheels, axles, and other LRV systems to ensure optimum operating efficiency consistent with design and management of requirements.Conducts routine inspection for major repairs, overhaul and preventive maintenance. Uses and operates various types of equipment including hand tools, power tools, measuring tools, diagnostic test equipment such as voltmeters, ohmmeters, wheel truing machines, wheel/axle press, tire press, fixtures, cranes, and any other specialized test or maintenance equipment necessary for the maintenance and repair of the light rail vehicles.Maintains up-to-date knowledge of electronic, pneumatic, hydraulic, electrical and mechanical principles as applied to LRV equipment and interprets technical publications, blueprints, source code manuals, wiring and circuit diagrams, etc. so as to be able to determine the cause of LRV problems and to make corrective repairs.Responsible for completing thorough equipment reports and records.Solves unusual and complex equipment malfunctions; performs necessary repairs.Operates special equipment not limited to re-railing equipment and portable jacks and other related duties as required.Upon successful completion of a limited operations examination, Electromechanic will move LRVs in the yard(s) and shop(s) necessary for maintenance and train make-up, etc. Such movements will require the operation of switches either manually or via control apparatuses.Operates trucks, high rail vehicles and similar equipment; pulls trailers.  Knowledge, Skills & Abilities   Knowledge of mechanical, electrical, and electronic theory and principles demonstrated by the successful completion of the qualifying period.Knowledge and understanding of maintenance and repair techniques acquired through experience as a skilled mechanic.Ability to successfully complete comprehensive technical exams administered during the LRV Electromechanic training program.Ability to work under limited supervision.Must maintain required training and certifications (including but not limited to Commercial Driver’s License).DOT physical (if required and not grand-fathered), and essential functions test for the safe operations and maintenance of trains (including tier training certifications, re-rail equipment training, and hi-rail equipment training).Must provide his/her tools.Ability to perform physical requirements of the job.               Successful completion of training program and post-training qualification periodEducation Experience Degree: High School or GED Years: 1 to 2 years   Field:  Filed: Transit Operations or Customer Service       Must be a least 21 years of age, able to pass a drug & alcohol screen, and able to obtain the required DOT certification.        Bi-State Development is committed to providing an Equal Employment Opportunity experience for all employees, applicants, vendors and customers with an environment free of discrimination, harassment, and retaliation.

focallength是什么

Must be a least 21 years of age, able to pass a drug & alcohol screen, and able to obtain the required DOT certification.

Focaldistance vsfocal length

The relation between the object distance (p), the image distance (q), and the focal length (f) of a thin lens is given by the lens equation:

FOV tofocal length

A concave lens by itself cannot form a real image on a screen, since it is a diverging lens. Hence, a different method must be used for measuring its focal length. This is done by placing the negative lens in contact with a positive lens of shorter focal length whose focal length is known. The equivalent focal length of the combination can be measured experimentally, and the focal length of the negative lens computed using equation (3).

Our fleet of more than 600 Metro Transit trains, buses and vans are operated, maintained, and protected by bus/van operators, security personnel, customer service, mechanics, and engineers—a team ranging widely in age, experience and professional specialty, but are united by shared passion for the community they serve.

When two thin lenses are in contact, the equivalent focal length of the combination may be measured experimentally by one of the above methods. It may also be calculated in terms of the individual focal lengths as:

Repeat this procedure for each of the convex lenses at your station. Record the data for each lens in an organized manner for later analysis. Also, pick any two convex lens and carefully place them into a single lens holder. Repeat the procedures for measuring focal length for this lens combination. Finally, place the concave lens and the shortest focal length convex lens together in a lens holder, and measure the focal length of this combination.

Focal lengthformula

focallength中文

Metro Transit provides transportation throughout the Bi-State area to tens of thousands of riders every day. These passengers rely on the Metro Transit system, and more than 2,000 Metro professionals to keep their life and their communities moving forward.

There are several lenses at your work station. Two of them are double concave lenses, and the rest of them are double convex. Take one of the convex lenses and measure its focal length by focusing a distant object or light source on the screen. Use an object four or more meters from the lens to do this accurately. Measure the distance from the lens to the screen where the image is sharply focused as the focal length of the lens. Record the distance in a data table. Do the same for each of the convex lenses at your station.

Focal length

The principal focal length of a converging lens may be determined by forming an image of a very distant object on a screen and measuring the distance from the lens to the screen. This distance will be the focal length, since rays of light from a very distant object are very nearly parallel. A more accurate method of determining the focal length of a positive lens is to measure the image distance corresponding to a suitable and known object distance, and to calculate the focal length from the lens equation (1).

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The magnification produced by a lens (the linear magnification) is defined as the ratio of the height of the image to the height of the object. This can be shown, by the use of geometry for similar triangles, to be equal to the ratio of the image distance to the object distance. Thus

Now you will determine the focal length of each lens by a different method, using the lens equation (1). Take the convex lens with the shortest focal length, and place it in a lens holder on the optical bench. Place the light source and grid object at one end of the optical bench, and place the white cardboard screen at a distance of about 5 times the focal length of the lens from the object, with the lens between the object and screen. Leave the object and screen fixed, and move the lens along the bench until a sharp image of the grid object forms on the screen. Measure the distance between the object and the lens, and between the lens and the screen, and record these in a data table. Also, measure the size of the image on the screen.

Measure the size of the grid object, and compute the magnification as the ratio of image size to object size for each set of data that you have. Compare this to the ratio of image distance to object distance (equation 2), using percent difference, for each data set. Look carefully at the two magnifications for the two positions of the same lens. What is the relationship between these magnifications?