凹透镜的会聚与发散

本文研究了影响凹透镜成像而产生会聚作用的几种因素，如介质折射率、透镜球面曲率半径等；给出了薄凹透镜发散／会聚临界角；辅助透镜临界物跑与两透镜焦距、两透镜距离的关系，从而澄清了凹透镜不能会聚产生实像的概念及产生实像的实质。     

“会聚”与“发散”(初二)

透镜有两种:凸透镜和凹透镜.凸透镜对光线有会聚作用,凹透镜对光线有发散作用.怎样理解凸透镜对光线的会聚作用和凹透镜对光线的发散作用呢?透镜对光线的会聚作用和发散作用与使光线变为会聚光线,发散光线的含义是不同的.     

几何光学中两种特殊的解题方法

例1在下图方框中填入适当的透镜． 学生往往不假思索地根据凹透镜对光线具有发散作用，在图1方框内填入凹透镜；根据凸透镜对光线有会聚作用在图2方框内填入凸透镜．实际两图都填错了．     

会聚呢?还是发散?(初二)

大家知道,凸透镜对光有会聚作用,凹透镜对光有发散作用.那么,下面两图方框中放的是凸透镜,还是凹透镜呢? 你也许看到光线经图1透镜后是发散的,经图2透镜后是会聚的,就断定前者是凹透镜,后者是凸透镜,但事实恰恰相反. 图1     

透镜对光线的会聚或发散辨析

众所周知,凸透镜对光线具有会聚作用,凹透镜对光线具有发散作用。能否说,凡是使光线会聚的透镜一定是凸透镜,能使光线发散的透镜一定是凹透镜呢?或者说任何光线经凸透镜后一定是会聚光线,经凹透镜后一定是发散光线呢? 如图1所示,有一条会聚光线,不经过透镜时会聚     

基于高斯成像公式测量凹透镜焦距在初中物理教学中的应用

透镜的焦距决定了其成像的品质和规律,是反映透镜特性的基本参数之一.对于凹透镜焦距的测量则是物理光学实验中的一项基本实验内容.本文中利用透镜的高斯成像公式来测量凹透镜的焦距,即借助一凸透镜得到所测凹透镜的虚物,该虚物经凹透镜成一实像于挡光板上,通过测量该凹透镜的虚物距和实像距,代入高斯成像公式求得焦距.改变凹透镜和挡光板...     

从光路判断透镜类型的一种简便方法

在初三物理“透镜及其应用”的教学中，我们发现学生对“凸透镜具有会聚作用“和“凹透镜具有发散作用”的理解是不多全面的，因此，在应用和判断使用的透镜类型时往往感到比较困难。学生对于路主轴干行的光线通过透镜发生的折射现多，比较容易得出“凸透镜具有会聚作用”和“凹透镜具有发散作用”的结论，如图1、图2。但是，如果人射光线是非平行光，学生就展难料校使用闲透镜类型。因为学生往往只根据人射光是平行时的折射现象将凸透镜的会聚作四片面理解为折射光线一定能“会聚于一点”；同样，也只是根据人射光是平行光时的折射现象将已…     

试谈透镜成像放大倍数与物距的关系

薄透镜分凸透镜与凹透镜,当透镜置于空气中时,它们的成像情况有三种:凸透镜成实像,凸透镜成虚像,凹透镜成虚像.因而透镜成像放大倍数与物距的关系也有三种情况.分别讨论如下:     

凸透镜为什么能会聚光线

两个面都磨成球面．或一个面是球面，另一个面是平面的光学器件叫透镜．透镜有两种．中间比边缘厚的透镜叫凸透镜．中间比边缘薄的透镜叫凹透镜．不同的透镜对光线的作用效果不同．从实验中我们可以看到凸透镜能够把平行光（比如太阳光）会聚到一点．而凹透镜则使平行光变得发散．可是为什么凸透镜对光线有会聚作用呢？课本中对此没有详细解释．只是提到“凸透镜是利用光的折射原理制成的光学器件”．     

论透镜的会聚与发散

现在绝大多数初中物理教材中关于透镜的描述都这样提到：“凸透镜对光线起会聚作用，凹透镜对光线起发散作用，”但如果细加推敲便会发现，此结论并不十分准确，有其局限性，如果条件适当，凸透镜也可以对光线起发散作用，凹透镜则可以对光线起会聚作用，下面我们就来具体分析，由于我们通常所研究的都是薄透镜，因此在下文中提到的透镜都是指薄透镜。     

Diversity study circles in teacher education practice: An experiential learning project

This paper addresses the dilemma of trying to prepare primarily white preservice teachers for educational arenas in which they will interface with students of colour and many who are socially disadvantaged. This paper describes how diversity study circles can be integrated as integral to education that is multicultural in the development of preservice teachers’ critical self-reflection as a bridge to developing a critical lens for classroom practice and a democratic society.     

Do instructional interventions influence college students’ critical thinking skills? A meta-analysis

Promoting students’ critical thinking skills is an important task of higher education. Colleges and universities have designed various instructional interventions to enhance students’ critical thinking skills. Empirical studies have yielded inconsistent results in terms of the effects of such interventions. This meta-analysis presents a synthesis of empirical studies designed to promote measurable changes in students’ critical thinking skills using instructional interventions. Findings demonstrated statistically significant but small average effect size and evidence of heterogeneity among studies. Hierarchical linear model was adopted to explore potential predictors of the variance across effect sizes. Results showed that student discipline and treatment length explained part of the variability among treatment effects. Limitations and implications are discussed.     

Critical thinking in education: a review

National governments and employers have argued that it is important for all sectors of education to prepare individuals who are able to think well and for themselves. 'Good thinking' and 'thinking well' are commonly used terms bound up with what is called 'critical thinking' in the research literature. Evidence is presented in this paper, however, which suggests that not all students may be good at critical thinking; nor do some teachers appear to teach students 'good thinking' skills. A review of the research literature in this area was undertaken and the methods and conceptions of teaching likely to inhibit and enhance critical thinking are outlined, as well as what is required to improve students' thinking skills. Ways forward in teaching critical thinking, and in helping students to learn to think well and for themselves, are described and discussed.     

A multi-level modeling approach to investigating students’ critical thinking at higher education institutions

Twenty-first century and higher-learning skills such as critical thinking are highly desired for new college graduates entering the workplace, especially with rapid changing technology and a more globalized economy. As a result, the importance of critical thinking development at higher education institutions has increased. The purpose of this study was to examine the effect of student and institutional variables on the difference in critical thinking scores between first-year and third/fourth-year students at higher education institutions. We examined the extent to which institutional variables moderate the relationship between student variables and the critical thinking score difference. We used a multi-level modeling approach to account for the clustering of students in institutions. Results of this study showed that: (a) institutional variability accounted for 15% of the variance in estimated critical thinking scores, (b) third/fourth-year students had higher critical thinking scores as compared to their first-year peers even when controlling for college admissions score, and (c) in the final model, the main effects of college admission scores, student-faculty ratio, and percent Black/African American were statistically significant; however, retention was the only significant moderator of the relationship between critical thinking scores and class level. Implications and future research are discussed.     

Joe L. Kincheloe: Embracing criticality in science education

This article reviews significant contributions made by Joe L. Kincheloe to critical research in science education, especially through a multimethodological, multitheoretical, and multidisciplinary informed lens that incorporates social, cultural, political, economic, and cognitive dynamics—the bricolage. Kincheloe’s ideas provide for a compelling understanding of, and insights into, the forces that shape the intricacies of teaching and learning science and science education. They have implications in improving science education policies, in developing actions that challenge and cultivate the intellect while operating in ways that are more understanding of difference and are socially just.

A method for predicting critical load evaluating adhesion of coatings in scratch testing

In this paper based on the experiment principle of evaluating adhesion property by scratch testing, the peeling mechanism of thin films is discussed by applying contact theory and surface physics theory. A mathematical model predicting the critical load is proposed for calculating critical load as determined by scratch testing. The factors for correctly evaluating adhesion of coatings according to the experimental data are discussed.     

A method for predicting critical load evaluating adhesion of coatings in scratch testing

INTRODUCTIONHardceramicfilmsdepositedbychemicalva pordeposition (CVD)andphysicalvapordeposi tion (PVD)techniqueshadbeenwidelyappliedinindustry .Coatingadhesionisaveryimportantpropertyforevaluatingthecoatingquality.Themethodevaluatingtheadhesionstrengthoft…     

Property of critical excitation for moment-resisting frames subjected to horizontal and vertical simultaneous ground motions

It has often been reported that, when building structures are subjected to near-fault earthquake ground motions, horizontal and vertical impulsive inputs may cause critical damage during the first few seconds. In practical design of building structures, however, the safety check, taking into account the effect of multi-component ground motions, is hardly conducted except the design of important structures such as high-rise buildings and nuclear power plants. Ftirthel＇more, it is not clear how the correlation of multi-component ground motions influences the actual safety of structures. In this paper, the detailed property of critical excitation is discussed in association with the relationship between the characteristics of ground motions and those of structures. The properties of various auto power spectral density （PSD） functions of the horizontal and vertical ground motions are investigated, and those of the critical cross PSD function of these two-directional ground motions are found by a devised algorithm in a feasible complex plane. A closed-form expression is derived from the critical relation of the auto PSD functions of the simultaneous inputs. This critical excitation method provides us with a new approach for earthquake-resistant design against the possible future earthquake which causes the critical damages to buildings.     

旋转二次曲面透镜基点和基面的位置确定

在光学仪器中,非球面透镜具有一定的实用价值,故对旋转二次曲面透镜光学性质的研究将有重要意义．根据等效光学系统理论和旋转二次曲面折射的焦距公式,并考虑了透镜两曲面的不同形状及不同曲率,导出了旋转二次曲面透镜的主距公式和焦距公式,统称为旋转二次曲面的基点位置公式．这些公式具有一般性,该文进行了分类讨论,最后给出了应用实例     

Hilbert空间中与弱拓扑有关的几个问题的探讨

在Hilbert空间中，引入了弱拓扑、强拓扑的基，可分、一致收敛、强收敛、弱收敛的概念，证明了Hilbert闭子空间是弱闭的，范数和内积的连续性，Hilbert空间的弱可分性，一致弱收敛性，单位球的弱紧性．