1 25. All forms of cytometry, depend on the basic laws of physics, including those of fluidics, optics, and electronics, most of which were established centuries ago. 300 bce), in his Optics, presented a law of reflection and discussed the propagation of light rays in straight lines. 2) n = c v. The ray nature of light is used to explain how light refracts at planar and curved surfaces; Snell's law and refraction principles are used to explain a variety of real-world phenomena; refraction principles are combined with ray diagrams to explain why lenses produce images of objects. Students majoring in Physics obtain broad-based knowledge and expertise applying these laws, as well as hands-on experience building electronic equipment and performing experiments, allowing them to pursue a wide range of educational and employment opportunities after graduation. Newton’s Opticks: Or, a Treatise of the Reflexions, Refractions, Inflexions and Colours of Light (1704) dominated the science of optics for more than a century. According to the first law of reflection, the angle of reflection equals the angle of incidence. Because the fibers are thin, light entering one is likely Kepler was born on 27 December 1571, in the Free Imperial City of Weil der Stadt (now part of the Stuttgart Region in the German state of Baden-Württemberg ). Particles of light are called photons. Mirrors are made by putting a thin layer of silver nitrate or aluminium behind a flat piece of glass. Figure 25. Two founding Refraction using Huygen’s principle. It is the topic of this chapter. 3: The Law of Reflection Reflection (physics) Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. (1) Using Huygens’ principle, verify the laws of reflection at a plane surface. Although, since light is an electromagnetic wave, other forms of electromagnetic radiation Feb 15, 1999 · Abstract. 4 Newton’s Third Law of Motion: Symmetry in Forces; 4. Consider a ray of light passing from medium 1 to medium 2 as shown in fig. 15: Optics is shared under a CC BY-NC-SA license and was authored, remixed, and/or curated by LibreTexts. The answer to this is quite complicated Jun 11, 2024 · Euclid (c. 5°, while water has an index of refraction of 1. Determining the focal lengths at collecting lenses using Bessel’s method. Feb 18, 2022 · Use the following optics equations for your imaging needs: Lateral magnification: Lateral magnification is one way you can describe how big the image is compared to the original object. 2. Table of Contents show. Thus n1 = 1. In quantum optics, light is assumed to have both wave and particle properties. 1 1. 1 11. Snell's law example 1. While René Descartes (1596–1650) is well-known as one of the founders of modern philosophy, his influential role in the development of modern physics has been, until the later half of the twentieth century, generally under-appreciated and under Jun 9, 2008 · Newton's wide range of discoveries, from his theories of optics to his groundbreaking work on the laws of motion and gravity, formed the basis for modern physics. In nonlinear optical parametric processes, conservation of photonic energy, momenta and parity often lead to selection rules, restricting the allowed polarization and frequencies of the emitted radiation. 1 Development of Force Concept; 4. This is intersected by a high-intensity light source Feb 20, 2022 · 27. Optics is the popular branch of physics which deals with the determination of behaviour and the properties of the light. Written by teachers for teachers and students, The Physics Classroom provides a wealth of resources that meets the varied needs of both students May 21, 2023 · What are the basic laws of optics? two basic laws of optics are the law of reflection: θ i = θ r (the angle of incidence is equal to the angle of reflection) and the law of refraction, also known as Snell’s law: n 1 sinθ 1 = n 2 sinθ 2 where n i refers to the refractive index of medium i and θ i is the angle between the normal and the The branch of optics that considers the behavior of light when it exhibits wave characteristics (particularly when it interacts with small objects) is called wave optics (sometimes called physical optics). This is a preview of optics. 2) (1. For our most up-to-date, mastery-enabled courses, check out high school physics and AP Physics! Introduction to physics Displacement, velocity, and time Acceleration. With Fermat Principle, that is, the most fundamental principle in geometric optics, it is easy to obtain the three laws of geometric optics as well as the paraxial refraction and The Laws of Refraction. To construct the following optical instruments: a) Slide projector; image scale to be determined. i. 01 Sep 2001. 5 Normal, Tension, and Other Examples of Forces; 4. Physics is also called " the fundamental science" because all branches of natural science like chemistry, astronomy, geology, and biology are constrained by laws of physics. In physical optics, light is assumed to behave like a classical wave. It can be divided into subdisciplines based on the type of model used to describe light. Refraction in water. Dividing both sides by N0 and taking the natural logarithm yields. Geometric optics. Image Oct 7, 2022 · two basic laws of optics are the law of reflection: θ i = θ r (the angle of incidence is equal to the angle of reflection) and the law of refraction, also known as Snell’s law: n 1 sinθ 1 = n 2 sinθ 2 where n i refers to the refractive index of medium i and θ i is the angle between the normal and the incident and …. Especially through systems made of lenses—pieces of glass or plastic shaped to alter the light passing through them—optics have made possible photography; the discovery of microorganisms through microscopes; the correction of some vision disorders by eyeglasses and contact lenses; the Overview. This chapter allso explains related concepts like- Huygens Principle , Brewster's Law and Coherent Sources To obtain numerical information, we use a pair of equations that can be derived from a geometric analysis of ray tracing for thin lenses. His most significant work involved forces and the development of a universal law of gravity. Gabriele C. 1: The law of reflection states that the angle of reflection equals the angle of incidence—θ r Oct 30, 2022 · Optics. Common examples include the reflection of light, sound and water waves. It also considers the interactions with the matter and also with the instruments which we need to detect it. Metrics. In concave mirrors; · Rays coming parallel to the principal axis pass from the focal point. 4 Applications of Thermodynamics: Heat Engines, Heat Pumps, and Refrigerators The two main laws of ray optics are – the law of reflection and the law of refraction. It is used in many areas of science, such as astronomy, engineering, oceanography, physics, and fiber optics. 2: Huygens's Principle - Diffraction. 00 here. Light is diffused when it reflects from a rough surface. Feb 1, 2023 · Important Derivations for Class 12 Physics Chapter 10 Wave Optics. Image length is half the radius of curvature. Nearsightedness and its Correction. Feb 20, 2022 · Summary. 3a, assuming medium 1 is air and given the incident angle is 30. 33 and a critical angle of 49°. · Rays coming from the focal point travel parallel to the principal axis. In communications, it is used to transmit telephone, internet, and cable TV signals. 6 Problem-Solving Strategies Sep 12, 2022 · This equation is known as Malus’s law. 5. Huygens' principle can be used to derive the law of reflection and the law of refraction. 16k Accesses. v 2 = speed of light in medium 2. 5 Citations. There are two laws that govern how light changes direction when it interacts with matter: the law of reflection , for situations in which light bounces off matter; and the law of refraction , for situations in which light passes through matter. When you place an object in front of a mirror, you see the same object in the mirror. An accurate technique for determining how and where waves propagate is given by Huygens’s principle: Every point on a wavefront is a source of wavelets that spread out in the forward direction at the same speed as the wave itself. The light is coherent if photons that compose the light are in-phase, and monochromatic if the photons have a single frequency (color). Physics: Optics Introduction. [60] Similarly, chemistry is often called the central science because of its role in linking Live Classes, Video Lectures, Test Series, Lecturewise notes, topicwise DPP, dynamic Exercise and much more on Physicswallah App. - Huygens' principle which states that each point on a wavefront is the source of 12. 1) (2. New experiments are pushing our understanding of light and optics to the limit and are also opening up new areas of physics and novel applications. Optics is the branch of physics concerned with the nature and uses of light. The first section places the MDPP. Science. 1: The law of reflection states that the angle of reflection equals the angle of incidence -- θr = θi θ r = θ i. Key Terms. It is called “geometric” optics because the images can be characterized using geometric constructions, such as ray diagrams. Learn. Ray Optics is all about the geometry of falling light. It is a vast science covering many simple and complex subjects ranging from the reflection of light off a metallic surface to create an image, to the interaction of multiple layers of coating to create a high optical density rugate notch filter . 9099. Jun 11, 2024 · optics, science concerned with the genesis and propagation of light, the changes that it undergoes and produces, and other phenomena closely associated with it. Figure 1. Browse videos, articles, and exercises by topic. Exercises and mastery mechanics will be removed from the physics archive in July 2024. 4 can be rewritten as. 3. · Ray hits the mirror at vertex, it reflects with the same angle it does Tasks. The characteristics of an image formed by a flat mirror are: (a) The image and object are the same distance from the mirror, (b) The image is a virtual image, and (c) The image is situated behind the mirror. So the laws of refraction state that the angle of incidence is the angle between the incident ray and the normal and the angle of refraction is the angle between the refracted ray and the normal. Descartes was a famously systematic philosopher and his Feb 20, 2022 · Large telescopes use reflection to form an image of stars and other astronomical objects. In accordance with Huygens’ principle, from each Jun 5, 2024 · Physics can, at base, be defined as the science of matter, motion, and energy. Popular applications of interferometry in industry include the measurement of small displacements, refractive index changes, and Reflection, refraction. Refraction and Snell's law. Physics archive. 2 Newton’s First Law of Motion: Inertia; 4. Lens systems 9. 100 ce ) undertook one of the first quantitative studies of the refraction of light as it passes from one transparent medium to another, tabulating pairs of angles of incidence and transmission for Jul 7, 2023 · Ray Optics is also called Geometrical Optics. His father, Heinrich Kepler, earned a precarious Jun 6, 2023 · Sir Isaac Newton invented calculus and explained optics. 3 Newton’s Second Law of Motion: Concept of a System; 4. f = R 2. Feb 20, 2022 · This chapter introduces the major ideas of geometric optics, which describe the formation of images due to reflection and refraction. The law of reflection is independent of wavelength, so mirrors do not have this problem. The wave nature of light came into existence to explain the other properties of light such as diffraction and interference. Sep 1, 2001 · Rewriting the laws of optics. Incident ray, reflected ray, refracted ray and the normal of the system lie in the same plane. This result is another advantage for the use of mirrors in optical systems such as telescopes. Light can travel in three ways from a source to another location: (1) directly from the source through empty space; (2) through various media; and (3) after being reflected from a mirror. Diamond has an index of refraction of 2. His grandfather, Sebald Kepler, had been Lord Mayor of the city. Optics usually describes the behavior of visible, ultraviolet, and infrared light. v 1 = speed of light in medium 1. Light approaching a mirror is termed an incident ray, and the beam of light that is reflected by the mirror is termed a reflected ray. 73 Altmetric. Our perception of color is not an objective measure of anything about the light Nov 17, 2023 · Conservation laws are one of the most generic and useful concepts in physics. Newton’s Laws of Motion: Sir Isaac Newton’s laws of motion laid the foundation for classical mechanics and our understanding of motion: Newton’s First Law (Law of Inertia): An object at rest remains at rest, and an object in motion continues to move at a constant velocity unless acted upon by an external In more advanced courses the laws are shown to result from the boundary conditions satisfied by the field vectors at a planar interface, which is then taken to provide justification for the laws. 000). We know that when a light travels from one transparent medium to another transparent medium its path changes. Substances that have a high index of refraction (n) have a low critical angle. The laws of physics are the starting point for most scientific research and engineering applications. Because light is a wave, the superposition principle is valid to determine the constructive Sep 12, 2022 · N = N0 2n. Modern ophthalmic lens making machine. First the wavefront touches the reflecting surface at B and then at the successive points towards C. Determining the focal lengths at collecting and dispersing lenses using collimated light. The word optics is derived from the Greek term Bookshelves. Therefore, sin θ c =. Unit 15: Geometric optics. He found that there is a constant relation between the angle of incident ray and The ray nature of light is used to explain how light reflects off of planar and curved surfaces to produce both real and virtual images; the nature of the images produced by plane mirrors, concave mirrors, and convex mirrors is thoroughly illustrated. 5: Reflection and Refraction. 42 with a critical angle of 24. Snell's law. In this chapter, we consider the phenomena of reflection, refraction and dispersion of light, using the ray picture of light. Both experiment, the observation of phenomena under conditions that are controlled as precisely as possible, and theory, the formulation of a unified conceptual framework The physics archive contains legacy physics content, and is not being updated with new content. 1) 1 d o + 1 d i = 1 f. To determine the relationship between these quantities, note that when t = T1 / 2, then N = N0 / 2. 6 Problem-Solving Strategies Optics is the study of the nature and behavior of light. Verifying the imaging laws with a collecting lens. This topic is important to optical engineers and electrical engineers in particular, but it is good for other disciplines to have at least a rudimentary understanding of …. Ptolemy ( c. This part of optics, described by straight lines and angles, is therefore called geometric optics. First published Fri Jul 29, 2005; substantive revision Fri Oct 15, 2021. Physical optics. Welcome to Physics Interactives! This section of our website features a collection of HTML5 interactive pages that allow a user to explore a physics concept. where v v is the observed speed of light in Huygens' principle for (a) a plane wave and (b) a spherical wave. Geometrical optics has to do with the We have seen that visible light is an electromagnetic wave; however, its wave nature becomes evident only when light interacts with objects with dimensions comparable to the wavelength (about 500 nm for visible light). 4. The present essay examines one of the cornerstones of Leibniz’s defense of teleology within the order of nature, namely, his derivation of the two central laws of geometrical optics from his ‘‘Most Deter-mined Path Principle’’ or ‘‘MDPP. Thick lenses 8. Derivations related to Huygens’ Principle. The index of refraction for air is taken to be 1 in most cases (and up to four significant figures, it is 1. Thus, Equation 10. Refraction Of Light. Objects don't have a color, they give off light that appears to be a color. Its laws are typically expressed with economy and precision in the language of mathematics. index of refraction: For a material, the ratio of the speed of light in vacuum to that in the material. Mirages are most commonly observed on sunny days when driving down a roadway. University Physics. Converging and diverging thin lenses 7. When light passes into a more central laws of geometrical optics, and a sampling of the optical phenomena he sought to explain. Strategy. From these laws, we can understand the behavior of optical devices such as telescopes and microscopes. Optics is a vast area of science covering multiple subjects, both simple and complex. Sep 12, 2022 · The law of reflection is illustrated in Figure 1. 35-1 (SJP, Phys 1120) Light and Optics: We just learned that light is a wave (an "electromagnetic wave", with verysmall wavelength). Download the App from Google Color is a function of the human visual system, and is not an intrinsic property. 2) and the theory of the classical optical instruments (the microscope, the History of optics. Strategy: The speed of light in a material, v v, can be calculated from the index of refraction n n of the material using the equation n = c/v n = c / v. · Ray coming from the center of curvature turn back on itself. May 21, 2024 · Class 12 Physics Notes for Chapter 10: Wave Optics The chapter- Wave Optics chapter includes the study of the relations between lights and wave that helps it to spread. Refraction of light at the interface between two media of different refractive indices, with n 2 > n 1. 9(b) above, it can be easily shown that there will be a critical angle θ c = sin -1 (n 1 /n 2 ) for a beam incident from n 2 such that the emergent beam Pure physics is a branch of fundamental science (also called basic science). 1) θ i = θ r. The reflected ray is always in the plane defined The Physics Classroom serves students, teachers and classrooms by providing classroom-ready resources that utilize an easy-to-understand language that makes learning interactive and multi-dimensional. A mirror is a reflective surface that light does not pass through, but bounces off of and this produces an image. Since the velocity is lower in the second medium (v 2 < v 1 ), the angle of refraction θ 2 is less than the angle of incidence θ 1; that is, the ray in the higher-index medium is closer to the normal. Solution. . Mar 10, 2015 · Isaac Newton was born on January 4, 1643, in Woolsthorpe, Lincolnshire, England. (Picture credit: Photodisc) Optics has always been the most pure and the most applied area of physics. Optics 101. 1. The three laws of geometric optics: The law of reflection defines that upon reflection from a smooth surface, the angle of the reflected ray is equal to the angle of the incident ray, with respect to the normal to the surface that is to a line perpendicular to the surface at the point of contact. Figure 27. Total internal reflection Jan 10, 2018 · This physics video tutorial provides a basic introduction into the law of reflection. e. In his work Physics, Aristotle intended to establish general principles of change that govern all natural bodies, both living and inanimate, celestial and terrestrial – including all motion (change with respect to place), quantitative change (change with respect to Definition: The law of reflection defines that upon reflection from a smooth surface, the angle of the reflected ray is equal to the angle of the incident ray, with respect to the normal to the surface that is to a line perpendicular to the surface at the point of contact. 3 Second Law of Thermodynamics: Entropy 12. Snell's law example 2. There are two major branches of optics, physical and geometrical. Communications Earth & Environment 3, Article number: 14 ( 2022 ) Cite this article. Since light always travels in a straight line and the direction in which light is propagated from the source is termed as the ray of light. To determine the focal length of a convex lens and of a combination of a convex and a concave lens using Bessel's method. Here are the equations: Locating images formed by mirrors: An object placed a certain distance away from a mirror will produce an image at a certain distance Introduction to Dynamics: Newton’s Laws of Motion; 4. More simply, it uses the interference these waves experience to make accurate measurements of the waves. Introduction to Dynamics: Newton’s Laws of Motion; 4. This unit is part of the Physics library. 1 sin θ c = n 2. Feb 20, 2022 · Find the index of refraction for medium 2 in Figure 25. We define the ratio of image height to object height ( hi / ho) as the magnification m. Optics that studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Laws of imaging. Introduction to optical Feb 20, 2022 · Fiber Optics: Endoscopes to Telephones. Reflection and refraction. See, for example, Bennett (1983; 1984, 213–230 Aug 16, 2021 · Example 11. Jan 25, 2022 · Climate change is physics. Total Internal Reflection. ’’. This article examines Isaac Newton’s contributions to the development of optics. The new wavefront is a line tangent to all of the wavelets. Here we present a new scheme to derive conservation laws in optical parametric processes in which many photons Optics. In this way, light is represented geometrically by rays, imaginary lines perpendicular to the light wave fronts. If the decay constant (λ) is large, the half-life is small, and vice versa. The reflected ray is always in the plane defined by the incident ray and May 24, 2024 · This gives us the law of reflection, which states that the incoming angle ( angle of incidence) equals the outgoing angle ( angle of reflection ): θi = θr (2. Some Interactives are simulations that allow a user to manipulate an environment and observe the effect of changes in variables upon the simulation. Simple optical instruments I: the eye and the magnifier, eyepieces and telescopes 10. Spectral power distributions exist in the physical world, but color exists only in the mind of the beholder. n 1. Jan 21, 2023 · The law of reflection states that the angle of reflection equals the angle of incidence: \[θ_r=θ_i \label{law of reflection} \] The law of reflection is illustrated in Figure \(\PageIndex{1}\), which also shows how the angle of incidence and angle of reflection are measured relative to the perpendicular to the surface at the point where the Physics Formulas Optics/Cheat Sheet. 1: Speed of Light in Matter. Optics is the branch of physics that deals with light and its properties and behavior. reflection: the property of a propagated wave being thrown back from a surface (such as a mirror) refraction: Changing of a light ray’s direction when it passes through variations in matter. Therefore, the laws of geometric optics only apply to light interacting with objects much larger than the wavelength of the light. His theory of colour and the compound nature of sunlight was central to modern optics. Note that the observed laws of geometric optics follow from the assumption that light is a wave. A laser is device that emits coherent and monochromatic light. 2. N0 2 = N0e − λT1 / 2. As you drive down the roadway, there appears to be a puddle of water on the road several yards (maybe one-hundred yards) in Aristotelian physics is the form of natural philosophy described in the works of the Greek philosopher Aristotle (384–322 BC). Specular and diffuse reflection 2. , the imaginary straight line drawn from the source used to understand the direction of propagation Jun 14, 2022 · Abstract. But primarily, one needs to know the basic terms. The law of reflection states that the angle of reflection equals the angle of incidence— \ ( {\theta }_ {\text {r}}= {\theta }_ {\text {i}}\). Spherical mirrors 12. The law of reflection states that the angle of incidence is equal to t Aug 14, 2020 · The retardation in a Pockels cell i s where is the 6-3 element of the electro-optic tensor. The Faraday effect: the polarization of light passing through material with length and to which a magnetic field is applied in the propagation direction is rotated by an angle where is the Verdet constant. May 21, 2024 · The geometrical optics is the branch of physics that focuses on studying how light spreads and is reflected when it passes from one medium to another, regardless of the effects of diffraction. 0 ∘. The son of a farmer who died three months before he was born, Newton spent most of his early years with his A mirage is an optical phenomenon that creates the illusion of water and results from the refraction of light through a non-uniform medium. This Open Source Physics animation helps you visualize the electric field vectors as light encounters a polarizing filter The extent to which change in direction takes place in the given set of a medium is termed as refractive index. The beauty of introducing rays is that from this point on, we can discuss sources and observers without a complicated reference to the spherical waves and Sep 3, 2021 · CLASS XII PHYSICS Chapter 7 - wave optics. The law of reflection says that for specular reflection (for example at a mirror Jul 29, 2005 · Descartes’ Physics. A large part of ray optics, including Gaussian optics (see Section 3. About this unit. Simple optical instruments II: light illuminators and microscope 11. Physics (Boundless) 4: The Laws of Motion. People thought about light as sort Basic laws of geometrical optics: experimental verification 6. The angles are measured relative to the perpendicular to the surface at the point where the ray strikes the surface. Physical optics deals primarily with the nature and properties of light itself. 0 ∘ and the angle of refraction is 22. Thus, optics describes the behaviours of visible light, infrared light as well as the ultraviolet. Determining the focal lengths at collecting lenses through autocollimation. Figure \(\PageIndex{6}\): A polarizing filter transmits only the component of the wave parallel to its axis, reducing the intensity of any light not polarized parallel to its axis. Calculate the speed of light in zircon, a material used in jewelry to imitate diamond. But in many cases, you can safely ignorethe wave nature of light! Light was studied for a long time (obviously), long before Maxwell, and very well understood. Other Interactives are skill building Light and Optics. We will conclude by noting a few of the many ways in which Descartes’ efforts in optics prompted – both through agreement and dissent – further developments in the history of optics. The Laws of Reflection in Geometric Optics: The conduct of the ray of light that is rebounded by a smooth mirror is judged based on the laws of reflection. 1) (24. Fiber optics employs the transmission of light down fibers of plastic or glass. When a gas in the laser absorbs radiation, electrons are elevated to different Jan 12, 2023 · Kerala Plus Two Physics Notes Chapter 9 Ray Optics and Optical Instruments. 2 First law of Thermodynamics: Thermal Energy and Work 12. 31 (a) shows chromatic aberration for a single convex lens, and its partial correction with a two-lens system. Newton's laws of motion are three physical and conservation laws was a key development in modern physics and can be conveniently to wave optics. Figure 16. The thin lens equation is: 1 do + 1 di = 1 f (24. Sep 12, 2022 · The speed of light depends strongly on the type of material, since its interaction varies with different atoms, crystal lattices, and other substructures. It was not until the advent of modern physics early in the 20th century that it was discovered that Newton’s laws of motion produce a good approximation to motion only when the objects are moving at speeds much, much less than the speed of light and when those objects are larger than the size of most molecules (about 10 − 9 m 10 − 9 m in Sep 10, 2021 · 14. By the time Johannes was born, the Kepler family fortune was in decline. Flow cytometry depends critically on the fluidics presenting each individual cell with precision to the sensing volume. The refractive index of medium 2 with respect to 1 can be written as Sep 12, 2022 · Describe the application of lasers to a CD and Blu-Ray player. Fiber optics is one application of total internal reflection that is in wide use. Optics is a branch of physics involved in the study of light, its behavior, and its properties. 1, which also shows how the angle of incidence and angle of reflection are measured relative to the perpendicular to the surface at the point where the light ray strikes. Using Snell's law for n 2 > n 1 in Fig. To determine the focal length of two unknown convex lenses by measuring the distances of image and object. This is as true now as at any time in history. Optics began with the development of lenses by the ancient Egyptians and Mesopotamians, followed by theories on light and vision developed by ancient Greek philosophers, and the development of geometrical optics in the Greco-Roman world. The document discusses various topics related to wave optics and the physics of light, including: - The wave nature of light and how it explains phenomena like reflection, refraction, the formation of shadows and spectra. It talks about the reflection of light off a metallic surface, image creation, the interaction of numerous coating layers to form a high optical density Abstract. Incident ray, coming from one medium to the boundary of another medium, is refracted with a rule derived from a physicist Willebrord Snellius. Feb 20, 2022 · The part of optics dealing with the ray aspect of light is called geometric optics. We can define a constant of a material that describes the speed of light in it, called the index of refraction n: n = c v (1. 12 Fundamental Laws of Physics: 1. 2 These soap bubbles exhibit brilliant colors when exposed to sunlight. When a ray of light encounters an interface between two transparent media, a portion of it is reflected and a portion is refracted, and it is natural to ask, even during an early introduction to the subject, just what fraction is reflected and what fraction is refracted. Hegerl. gp ij rb aa uo ej xj mg aa ms