laser essays

laser essays Before we can learn about the laser we need to know a little bit about light (since that is what a laser is made of). Light from our sun, or from an electric bulb, is called white light. It is really a mixture of all the different colours of light. The colours range from violet, indigo, and blue, to green, yellow, orange, and red. These make up the visible part of the electromagnetic spectrum. Light is made up of particles, called PHOTONS, which travel in waves. The difference in the colour depends on the wavelength of the light. Violet light has the shortest wavelength while red has the longest. There are other parts of the electromagnetic spectrum which includes infra-red, radar, television radio and micro- waves (past red on the spectrum), and on the other end of the spectrum are the other invisible radiations, ultra- violet, X rays, micro waves and gamma rays. The wavelength of the light is important to the subject of the laser. A laser is made up of COHERENT light, a special kind of light in which the wavelengths of the light are all the same length, and the crests of these waves are all lined up, or in PHASE. The word Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. What does that mean? Basically a laser is a device which produces and then amplifies light waves and concentrates them The principles of the laser (and it's cousin the maser) were established long before these devices were successfully developed. In 1916 Albert Einstein proposed stimulated emission, and other fundamental ideas were discussed by V.A. Fabrikant in 1940. These ideas, followed by decades of intensive development of microwave technology set the stage for the first maser (a laser made up of micro-waves), and this in turn helped to produce more advances in this area of science. These efforts cumulated in July 1960 ...

English Verb Tense Resources

English Verb Tense Resources Learning verb tenses is one of the most important tasks in any language learning. There are a number of resources at the site that will help you learn tense rules, practice using verbs in different tenses, read sample sentences in a variety of tenses, teach tenses in class, and more. For an overview of conjugation of all these tenses, use the tense tables or the visual guide to tenses for reference. Teachers can use theses guides on how to teach tenses for further activities and lesson plans in class Tense Use Rules and Explanations These explanation resources provide the rules for each tense, as well as examples of proper tense use. Use the time expression commonly used with the tense, as well as the example sentences to help you get started. Present Simple Every day - When do you get up? / Tom usually eats lunch at home.Present Continuous Now - Shes watching TV at the moment. / Im not working, Im reading a newspaper.Past Simple Yesterday - They went on vacation last July. / Where did you meet Tim?Past Continuous Yesterday, at X oclock They were watching TV at 5 oclock yesterday. / What were you doing when he came home?Present Perfect Since / For - Ive lived here a long time. / Have you ever seen that film?Past Simple vs. Present Perfect Ive lived here for many years. vs. I lived there before I moved to New York.Present Perfect Continuous Since / For Time - Weve been working since 8 this morning. / What has she been doing recently?Past Perfect Already - They had already eaten when she arrived. / Had you finished the report by the time he asked for it?Future with Will Tomorrow, Next week - Well get together next week. / Will you be able to come tomorrow?Future with Going to Tomorrow, Next year, semester, etc. - Theyre goi ng to study Russian next semester. / Where are you going to stay?Future Perfect By, By the time - Ill have finished by the time he arrives. / Will you have done the work by six?Future Continuous At X oclock, This time next year, month, week / What will you be doing this time next year? - Shell be working tomorrow at 10 oclock.Conditional Forms If questions - What would you do if you had enough time? / If she is in town, shell come to the meeting.Alternate Conditional FormsModal Forms Asking Permission, Giving Advice, etc. - May I help you? / He should see a doctor.Modal Verbs of Probability Stating guesses - He must have stayed at home today. / She might be downstairs. Tense Use Rules For Beginners These tense explanations cover basic tenses and are especially for beginners. They include easier English as well as example dialogues of tense use. Present SimplePast SimplePresent PerfectFuture with WillFuture with Going toModal Form Basics Tense Quizzes Once you understand the tense use, these quizzes will help you test your knowledge. The more you practice, the more confident you will feel using various tenses. Past Tenses ReviewSimple Past or Present PerfectPresent Perfect or Present Perfect ContinuousAdvanced Tense IdentificationConditional FormsPassive Forms Quiz Tense Review If you have a good understanding of tense use, these pages will help you review tenses as they relate to each other. The resources include a tense timeline, and a special section focusing on auxiliary verbs - the key to verb conjugation. English Tenses TimelinePresent Tense Auxiliary VerbsPast Tense Auxiliary VerbsFuture Tense Auxiliary VerbsSimple vs. Progressive VerbsExample Sentences in All Tenses Tense Use Lessons These lesson plans can be used in your classes. Each lesson plan includes an introduction, a step by step guideline to teaching tense use, and class exercises to be used during the lesson. A Difficult Situation: Using Modal Verbs of Probability in the PastA VIP - Present Perfect Simple and Continuous Lesson PlanConditional StatementsIntegrating Past ContinuousPassive VoiceTense ReviewTime Expressions and Simple Past or Present PerfectReported Speech: Developing Production SkillsTense Review for Advanced Levels