Mi calendario de la semana: Listen to Alejandro describing h…
Mi calendario de la semana: Listen to Alejandro describing his classes schedule for the week. Answer the questions, and select if the statement is true (cierto) or false (falso). Javier estudia con sus amigos el viernes a las siete de la noche
Read DetailsTIEMPO PRESENTE VERBOS TERMINADOS EN “AR”: Conjugue los verb…
TIEMPO PRESENTE VERBOS TERMINADOS EN “AR”: Conjugue los verbos dados en paréntesis en tiempo presente para completar el sentido del texto. (PRESENT TENSE “AR’ VERBS: conjugate the verbs in parentheses in present tense to complete the meaning of the text). Mis amigos Juan, Luis y Ana _______ (regresar) de sus vacaciones mañana, y yo _______ (estar) muy feliz pues son mis amigos de toda la vida. Nosotros _______ (estudiar) juntos toda nuestra escuela primaria y secundaria y ahora Luis y Juan _______ (estar) estudiando juntos en Valencia, Ana _______ (tomar) un año de descanso y ella también _______ (trabajar) unas horas en la Biblioteca Pública, pues _______ (necesitar) dinero para comprar un carro. Luis y Juan _______ (pasar) el día juntos pues tienen pasatiempos muy artísticos. Luis _______ (pintar) cuadros en acuarela y Juan _______ (cantar) que es una belleza. Ellos _______ (practicar) después de las clases. Ana es una chica muy convencional, ella _______ (escuchar) música en todo momento , y también _______ (bailar) en sus ratos libres. Yo soy una chica muy alegre y _______ (estudiar) música, ya que desde pequeña _______ (tocar) piano, y además yo también _______ (tomar) clases de japonés. ¡Extrañaba (I missed them) mucho a mis amigos!
Read DetailsHAY – LOS NÚMEROS: Look at the report and answer the questio…
HAY – LOS NÚMEROS: Look at the report and answer the questions with in short sentences. (Write the numerals as words, use capital letter for the first word, and pay attention to the accent marks). Model: ¿Cuántos chicos hay? Hay cinco chicos. Estudiantes en el Club de Español Actividades 1 número total de estudiantes: 21 Lecturas: 17 2 número de chicos: 5 Textos escritos: 23 3 número de chicas: 16 Profesores invitados: 9 1. ¿Cuántos estudiantes en total hay?
Read DetailsProblem 1 (30 points) (a) (10 points) What are the basic com…
Problem 1 (30 points) (a) (10 points) What are the basic components that are necessary to make a laser? Describe briefly the function of each component listed. (b) (5 points) Should you expect gas lasers at relatively low pressure to have emission spectral lineshapes that are dominated by homogeneous broadening or inhomogeneous (i.e. Doppler) broadening? Explain your reasoning. (c) (15 points) Q-switching (i) Qualitatively describe Q-switching and how it is used in laser systems. (ii) What are two methods of accomplishing Q-switching? (iii) What are typical pulse duration and peak power values for Q-switched lasers? Problem 2 (30 points) The L-Shaped Cavity of a Nd:YVO4 laser is shown below. Answer the following questions. Assume the cavity(except the Nd:YVO4 crystal) is filled with air. (a) (10 points) Calculate the free spectral range(FSRυ) for the cavity in MHz. (b) (5 points) For a light source at 532 nm what is the spacing (FSRλ , in terms of wavelength) between the longitudinal modes? (c) (5 points) What is the Finesse of the cavity? (d) (10 points) The gain medium above can be described by a four level system shown below. Sketch the approximate population densities (N2 and N1) for the given lifetime ratios and pump intensities. Provide a brief explanation explaining solution. You may sketch and label the population densities on the plot provided for each case. Initial population of states 1 and 2 can be assumed to be 0. State any additional assumptions you make, if required. Problem 3 (40 points) In the laser system shown below, only state 2 is pumped directly from the ground (or 0) state with a pumping value of R2 (cm-3/sec). State 2 decays to 0 at a rate of 5 x 106 sec-1 and to 1 by spontaneous emission (A21) and quenching collisions (k21) at a total rate (A21+k21) of 107 sec-1. The lifetime (τ1) of state 1 is 50ns. Assume homogeneous broadening; line width Δυ = 2 cm-1(= 60 GHz), λ= 400 nm; A21 = 106 sec-1; M= 40 x 1.67 x 10-27 kg; T=500K and that the medium fills the cavity in the manner shown below. Also assume steady state. (a) (10 points) What is the stimulated emission cross section at line center? (b) (10 points) Estimate the population inversion necessary to bring the laser to threshold? (c) (10 points) Write down the rate equations for the system described and calculate the steady state population densities N2 and N1. (d) (10 points) What is the pump rate needed to bring the laser to threshold? (Hint: gi=2Ji+1) Congratulations, you are almost done with this exam. DO NOT end the Honorlock session until you have submitted your work. When you have answered all questions: Use your smartphone to scan your answer sheet and save the scan as a PDF. Make sure your scan is clear and legible. Submit your PDF as follows: Email your PDF to yourself or save it to the cloud (Google Drive, etc.). Click this link to go to Gradescope: Final Exam Return to this window and click the button below to agree to the honor statement. Click Submit Quiz to end the exam. End the Honorlock session.
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