DOCSLIB.ORG

Chapter 24: Geometrical Optics

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Chapter 24: Geometrical Optics Nature of Light Ancient times & Middle Ages: light consist of stream of particles corpuscles 19th century: light is a wave (EM wave) Geometrical optics 20th century: several effects associated with the emission and absorption of light revel that it also has a particle aspect and that the energy carried by light waves is packaged in Chapter 24 discrete bundles called photons. Quantum electrodynamics – a comprehensive theory that includes both wave and particle properties. The propagation of light is best described by a wave model The emission and absorption by atoms and nuclei requires a particle approach Wave Fronts Rays Wave Front – a convenient concept to describe wave It is very convenient to represent propagation a light wave by rays rather than A wave front is the locus of all adjacent points at which by wave fronts the phase of vibration of the wave is the same A ray is an imaginary line along the direction of travel of the wave The branch of optics for which the ray description is adequate is called geometric optics The branch dealing specifically with wave behavior is called physical optics spherical and planar wave fronts and rays Reflection and Refraction When a light ray travels from one medium to another, Part 1 part of the incident light is reflected and part of the light is transmitted at the boundary between the two media. The transmitted part is said to be refracted in the The reflection of light second medium. incident ray reflected ray refracted ray 1 Types of Reflection If the surface from which the light is reflected is smooth, then the light undergoes specular reflection (parallel rays will all be reflected in the same directions). If, on the other hand, the surface is rough, then the light will undergo diffuse reflection (parallel rays will be reflected in a variety of directions) Eduard Manet – A Bar at the Foleis-Bergère (1882) Types of Images for Mirrors and Lenses The Law of Reflection A real image is one in which light actually passes through the image point For specular reflection the incident angle θi equals the reflected angle θ : Real images can be displayed on screens r A virtual image is one in which the light does not pass through the image point θi = θr The light appears to diverge from that point Virtual images cannot be displayed on screens The angles are measured relative to the normal as shown. Plane Mirrors Forming Images with a Plane Mirror A mirror is a surface that can reflect a beam of light in A plane mirror is simply a flat mirror. one direction instead of either scattering it widely in Consider an object placed at point P in front of a plane many directions or absorbing it. mirror. An image will be formed at point P´ behind the mirror. do = distance from object to mirror di = distance from image to mirror ho = height of object hi = height of image ho hi For a plane mirror: do di do = di and ho = hi 2 Plane Mirrors What is wrong with the painting? A plane mirror image has the following properties: 9 The image distance equals the object distance 9 The image is unmagnified 9 The image is virtual 9 The image is not inverted Conceptual Checkpoint To save expenses, you would like to buy the shortest mirror that will allow you to see your entire body. Should the mirror be equal to your height? Part 2 Does the answer depend on how far away from the mirror you stand? Spherical Mirrors Spherical Mirrors Concave Mirror, Notation A spherical mirror is a mirror concave whose surface shape is • The mirror has a radius spherical with radius of curvature of curvature of R • Its center of curvature is R. There are two types of the point C spherical mirrors: concave and • Point V is the center of convex. the spherical segment We will orient the mirrors so that • A line drawn from C to V is called the principle the reflecting surface is on the axis of the mirror left side of the mirror. The object will be to left of the mirror itself. convex 3 Focal Point Focal Length Shown by Parallel Rays When parallel rays are incident upon a spherical mirror, the reflected rays intersect at the focal point F. For a concave mirror, the focal point is in front of the mirror. For a convex mirror, the focal point is behind the mirror. The incident rays diverge from the convex mirror, but they trace back to the focal point F. Focal Length Ray Tracing The focal length f is the distance from the surface of the We will use three mirror to the focal point. It can be shown that the focal principal rays to length is half the radius of curvature of the mirror. determine where an image will be Sign Convention: the focal length is negative if the focal located. point is behind the mirror. For a concave mirror, f = ½R The parallel ray (P ray) reflects For a convex mirror, f = −½R (R is always positive) through the focal point. The focal ray (F ray) reflects parallel to the axis, and the center-of-curvature ray (C ray) reflects back along its incoming path. Ray Tracing – Examples More examples: Images from spherical mirrors concave convex Real images form on the side of the mirror where the object is, and virtual images form on the Virtual image Real imageopposite side 4 Ray Diagram for Concave Mirror, p > R • The image is real • The image is inverted • The image is smaller than the object Ray Diagram for a Concave Mirror, p < f Ray Diagram for a Convex Mirror • The image is virtual • The image is virtual • The image is upright • The image is upright • The image is larger than the object • The image is smaller than the object Spherical Aberration Image Formed by a Concave Mirror • Mirror is not exactly spherical • Geometry shows the • This results in a blurred relationship between image the image and object • This effect is called distances spherical aberration 112 + = pq R This is called the mirror equation 5 problem The Mirror Equation Sign Conventions: di is positive if the image is in Example 1 The ray tracing technique front of the mirror (real image) shows qualitatively where the di is negative if the image is image will be located. The behind the mirror (virtual An object is placed 30 cm in front of a concave mirror of distance from the mirror to the image) radius 10 cm. Where is the image located? Is it real or image, di, can be found from virtual? Is it upright or inverted? What is the magnification f is positive for concave mirrors the mirror equation: of the image? f is negative for convex mirrors 1 1 1 + = m is positive for upright images 11111 1 += += d 6 do di f m is negative for inverted images m =−i =− =−0.2 dd0 ii f30 d⎛⎞10 ⎜⎟+ d0 30 2 image magnification. If m is ⎝⎠ Image is smaller, real and inverted. do = distance from object to negative, the image is inverted 111 530× mirror =−or di = =6 cm (upside down). di 530 305− di = distance from image to mirror image height h d m = = i = − i f = focal length object height ho do problem problem Example 2 Example 3 An object is placed 5 cm in front of a convex mirror of An object is placed 3 cm in front of a concave mirror of radius focal length 10 cm. Where is the image located? Is it real 20 cm. Where is the image located? Is it real or virtual? Is it or virtual? Is it upright or inverted? What is the upright or inverted? What is the magnification of the image? magnification of the image? 11111 1 d 3.33 + =+=− m =−i = =0.67 11111 1 d 4.3 dd0 ii f510 d += += i d0 5 20 m =− = =1.43 dd0 ii f3 d⎛⎞ d 3 111 ⎜⎟ 0 or Image is smaller, virtual, and upright. ⎝⎠2 =− − Image is larger, virtual, and upright. di 10 5 111 310× = −or d =− =−4.3 cm 510× d 10 3i 7 d =− =−3.33 cm i i 15 problem Problem A concave mirror produces a virtual image that is three times as tall as the object. (a) If the object is 22 cm in front of the mirror, what is the image distance? (b) What Part 3 is the focal length of this mirror? The Refraction of Light d i 111111 am.) =− b.) += −= d0 dd0 i f22 66 f d 366=−i d =− cm66× 22 22 i f ==33 cm 66− 22 6 The Refraction of Light Snell’s Law In general, when light enters a new material its direction will change. The angle of refraction θ2 is related to the angle of The speed of light is different in different materials. We incidence θ by Snell’s Law: 1 sinθ sinθ define the index of refraction, n, of a material to be the ratio 1 = 2 of the speed of light in vacuum to the speed of light in the v1 v2 where v is the velocity of light in the medium. material: c n = Normal line v θ When light travels from one medium to another its velocity Snell’s Law can also be written as 1 and wavelength change, but its frequency remains n1 sinθ1 = n2 sinθ2 Air constant. For a vacuum, n = 1 The angles θ1 and θ2 are Glass measured relative to the line For other media, n > 1 θ normal to the surface between 2 n is a unitless ratio the two materials.
Load more

Recommended publications
  • Mirror Images Georg Maier
    Mirror Images Georg Maier The following article is excerpted from Chapter 3 of An Optics of Visual Experience, by Georg Maier. The text has been abridged and adapted for In Context. See the box on next page and the end of the article for further information. hen we see a rock in the landscape we feel sure that it is “really there!” Seeing is usually experienced almost like touching. Sight helps us to orient ourselves in our surroundings when we set off toward an as yet dis- tant goal, just as it lets us attend to our activities right here where we are. Thus seeing is generally thought to simply be our ability to keep an eye on objects. WAny attempt to use mirror images to orient ourselves in a similar way will lead to confusion. They do not seem to corre- spond to our other perceptions of bodies with respect to their location. They offer “extra,” “indirect” views, and as long as we are not clear about what we mean here by “indirect,” we will justifiably claim that they are unreal for us. In the following considerations the object that is mirrored will be referred to as the prototype. Our main task will be to understand the lawful relationships between mirror images and their prototypes. Mirror Images in a Quiet Pond It is worthwhile to study reflections in quite some detail in a moderately-sized pond. Memorable key experiences can be gained in such a situation. If the pond is small and sheltered from wind, its surface will normally be quiet.
    [Show full text]
  • Infrared Deflectometry for the Inspection of Diffusely Specular Surfaces
    Adv. Opt. Techn. 2016; 5(5-6): 377–387 Review Article Open Access Sebastian Höfer, Jan Burke* and Michael Heizmann Infrared deflectometry for the inspection of diffusely specular surfaces DOI 10.1515/aot-2016-0051 principles of thermal deflectometry, its special challenges, Received September 12, 2016; accepted November 5, 2016; previously and illustrates its use with examples from the inspection published online December 8, 2016 of industrially produced surfaces. Abstract: Deflectometry is a full-field gradient technique Keywords: deflectometry; infrared displays; metrological that lends itself very well to testing specular surfaces. It instrumentation. uses the geometry of specular reflection to determine the gradient of the surface under inspection. In consequence, a necessary precondition to apply deflectometry is the 1 Introduction presence of at least partially specular reflection. Surfaces with larger roughness have increasingly diffuse reflection This section presents the basic ingredients needed for characteristics, making them inaccessible to usual deflec- understanding the technique of deflectometry and appre- tometry. However, many industrially relevant surfaces ciating the rationale for extending the wavelength range exist that change their reflection characteristic during into the infrared. production and processing. An example is metal sheets that are used as car body parts. Whereas the molded but otherwise raw metal sheets show a mostly diffuse reflec- 1.1 Deflectometry tion without sufficient specular reflection, the final car body panels have a high specular reflectance due to the When testing and/or measuring reflective objects, the lacquering. In consequence, it would be advantageous well-established technique of fringe projection [1] is not to apply the same inspection approach both for the raw available because there is not enough scattered light avail- material and for the final product.
    [Show full text]
  • Geometrical Optics / Mirror and Lenses Outline Reflection Plane Mirrors Concave/Convex Mirrors Refraction Lenses Dispersion Geometrical Optics
    Geometrical Optics / Mirror and Lenses Outline Reflection Plane Mirrors Concave/Convex Mirrors Refraction Lenses Dispersion Geometrical Optics In describing the propagation of light as a wave we need to understand: wavefronts: a surface passing through points of a wave that have the same phase and amplitude. rays: a ray describes the direction of wave propagation. A ray is a vector perpendicular to the wavefront. Reflection and Refraction When a light ray travels from one medium to another, part of the incident light is reflected and part of the light is transmitted at the boundary between the two media. The transmitted part is said to be refracted in the second medium. http://www.geocities.com/CapeCanaveral/Hall/6645/propagation/propagation.html *In 1678 the great Dutch physicist Christian Huygens (1629-1695) wrote a treatise called Traite de la Lumiere on the wave theory of light, and in this work he stated that the wavefront of a propagating wave of light at any instant conforms to the envelope of spherical wavelets emanating from every point on the wavefront at the prior instant. From this simple principle Huygens was able to derive the laws of reflection and refraction incident ray reflected ray refracted ray Types of Reflection When light reflects from a smooth surface, it undergoes specular reflection (parallel rays will all be reflected in the same direction). When light reflects from a rough surface, it undergoes diffuse reflection (parallel rays will be reflected in a variety of directions). The Law of Reflection For specular reflection the incident angle θi equals the reflected angle θr: θi =θr (Known since 1000 BC) The angles are measured relative to the normal, shown here as a dotted line.
    [Show full text]
  • False Reflections
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Apollo Penultimate draft. Forthcoming in Philosophical Studies Please cite published version, available at Springer via http://dx.doi.org/ 10.1007/s11098-016-0752-x FALSE REFLECTIONS by Maarten Steenhagen Standing in front of a bathroom mirror, looking straight ahead, you seem to see your own face. You seem to be able to look at your countenance from where you are. But of course your face is not there, where you see it; it is not on the other side of the mirror. It is where you are, on this side of the mirror. That should be obvious to anyone familiar with mirror re- flections. Some, however, take this to be one respect in which mirror appearances are illus- ory. They deem it obvious that what you see in an ordinary plane mirror appears to be over there, behind the mirror’s surface, while it is not in fact located there. For this reason they take mirrors to introduce some kind of optical illusion to visual experience. Call this view specular illusionism.1 Specular illusionism may seem like an entirely natural position to arrive at. Yet its natural- ness obscures the possibility of reasonable disagreement over whether this view is plausible or even correct. Here I will show that the specular illusionist’s claim rests on substantive as- sumptions about how things must appear to us; assumptions that fall within the purview of philosophical catoptrics, the philosophical study of the optical properties of mirrors.
    [Show full text]
  • Lecture 15 Reflection & Refraction
    LECTURE 15 REFLECTION & REFRACTION 18.1 The ray model of light Endoscopes use fiber optics. Seeing objects Shadows 18.2 Reflection The plane mirror 18.3 Refraction Total internal reflection Learning objectives 2 Use the ray model of light—how light is emitted from objects, how we see objects, and how shadows are formed. Use the law of reflection to locate images formed in plane mirrors. Apply the laws of reflection and refraction to relate indices of refraction, and angles of incidence, reflection, and refraction. Describe how total internal reflection occurs and calculate or use the critical angle. 18.1 Seeing objects / Demo Demo: Laser beam Why can you not see the laser beam? In order for our eye to see an object, rays from that object must enter the eye. https://tvtropes.org/pmwiki/pmwiki.php/Main/LaserHallway Group exercise: 18.1-1 (Evolution of eyes) 4 a) The eye can sense light and dark. b) How does this eye allow directional sensitivity? Group exercise: 18.1-1 (Evolution of eyes) answer 5 a) The eye can sense light and dark. b) How does this eye allow directional sensitivity? Evolution of eyes 6 c) Pinhole eyes have tradeoff of light collection and sharp imaging. d) Humor allows refraction to converge rays. f) Our eyes see by focusing a bundle of rays using lens. 18.1 Shadows An opaque object can intercept rays, creating a shadow behind it. A point source creates a completely dark shadow with a sharp edge. An extended source often creates a true shadow that no light reaches, surrounded by a fuzzy region of increasing brightness.
    [Show full text]
  • Basic Geometrical Optics
    FUNDAMENTALS OF PHOTONICS Module 1.3 Basic Geometrical Optics Leno S. Pedrotti CORD Waco, Texas Optics is the cornerstone of photonics systems and applications. In this module, you will learn about one of the two main divisions of basic optics—geometrical (ray) optics. In the module to follow, you will learn about the other—physical (wave) optics. Geometrical optics will help you understand the basics of light reflection and refraction and the use of simple optical elements such as mirrors, prisms, lenses, and fibers. Physical optics will help you understand the phenomena of light wave interference, diffraction, and polarization; the use of thin film coatings on mirrors to enhance or suppress reflection; and the operation of such devices as gratings and quarter-wave plates. Prerequisites Before you work through this module, you should have completed Module 1-1, Nature and Properties of Light. In addition, you should be able to manipulate and use algebraic formulas, deal with units, understand the geometry of circles and triangles, and use the basic trigonometric functions (sin, cos, tan) as they apply to the relationships of sides and angles in right triangles. 73 Downloaded From: https://www.spiedigitallibrary.org/ebooks on 1/8/2019 DownloadedTerms of Use: From:https://www.spiedigitallibrary.org/terms-of-use http://ebooks.spiedigitallibrary.org/ on 09/18/2013 Terms of Use: http://spiedl.org/terms F UNDAMENTALS OF P HOTONICS Objectives When you finish this module you will be able to: • Distinguish between light rays and light waves. • State the law of reflection and show with appropriate drawings how it applies to light rays at plane and spherical surfaces.
    [Show full text]
  • Chapter 26 Geometrical Optics Chapter 26 Geometrical Optics
    Chapter 26 Geometrical Optics Outline 26-1 The Reflection of Light 26-2 Forming Images with a Plane Mirror 26-3 Spherical Mirror 26-4 Ray Tracing and the Mirror Equation 26-5 The Refraction of Light 26-6 Ray Tracing for Lens 26-7ThiL7 Thin Lens Equa tion 26-1 The Reflection of Light Light propagation can be described in terms of “wave front” and “rays”. Wave front is mostly associated with physical optics (difficult to understand), while rays are mostly associated with geometrical optics (easy to understand). Wave front: Think about water wave! Figure 26-1 Wave Fronts and Rays of a point light source • The rays are always traveling in straight line and they indicate the traveling direction of the light--- in Geometrical Optics! • Rays are always at right angle to the wave fronts. More wave fronts Figure 26-2 Spherical (point source light) and Planar (sun light) Wave Fronts In ggpeometrical optics,,y a few rays are used for the representation of the light traveling. The Law of Reflection Figure 26-3 Reflection from a Smooth Surface The Law of Reflection θr = θi The angle of reflection is equal to the angle of incidence (Fig 26-3). The applications of Reflection Law • Reflection on smooth surface (figure a): Specular reflection. • Reflection on rough surface (figure b): Diffuse reflection. Figure 26-4 Reflection from Smooth and Rough Surfaces 26-2 Forming Images with a Plane Mirror Imaging process of the human eye: The imaging process of human is a point – to – point matching process between the distant object and the retina image, in which the image is focused by the eye “lens on the retina for sensing.
    [Show full text]
  • 2 Reflection, Refraction, Diffraction, and Scattering
    2 Reflection, refraction, diffraction, and scattering In this chapter we will describe how radiation is reflected off a surface, transmitted into a medium at a different angle, how it is influenced by passing an edge or through an aperture, and how it is scattered and spread out by interactions with particles at various scales. We will focus on the propagation of light. In order to describe the direction in which light propagates, it is often convenient to represent a light wave by rays rather than by wave fronts. In fact, rays were used to describe the propagation of light long before its wave nature was established. Geometrically, the duality is easy to handle: Whenever we indicate the direction of propagation of light by a ray, the wave front is always locally perpendicular to the ray. 2.1 Reflection Figure 2-1. Spheres reflected in the floor and in each other. Reflection occurs when a wave hits the interface between two dissimilar media, so that all of or at least part of the wave front returns into the medium from which it originated. Common examples are reflection of light, as shown in figure 2-1, as well as reflection of surface waves that may be observed in a pool of water, or sound waves reflected as echo from a wall. Reflection of light may be specular or diffuse. The first occurs on a blank mirroring surface that retains the geometry of the beams of light. The second occurs on a rougher surface, not retaining the imaging geometry, only the energy. © Fritz Albregtsen 2008 2-2 Reflection, refraction, diffraction, and scattering 2.1.1 Reflectance Reflectance is the ratio of reflected power to incident power, generally expressed in decibels or percent.
    [Show full text]
  • Geometrical Optics Mirrors and Prisms Mirrors
    Phys 322 Lecture 14 Chapter 5 Geometrical Optics Mirrors and Prisms Mirrors Ancient bronze mirror Liquid mercury mirror Hubble telescope mirror Planar mirror also called plane, or flat mirrors s = -s i r i o Sign convention: s on the object side is positive, and negative on the opposite side Planar mirror Sign convention: s on the object side is positive, and negative on the opposite side si = -so For a plane mirror, a point source and its image are at the same distance from the mirror on opposite sides; both lie on the same normal line. Image is virtual, up-right, and life-size (MT = +1) yi si The equation for lens works: MT yo so Exercise: plane mirror height How high should be the mirror for a person to see a full image of him/her-self? D Solution: B A C E Triangle ABC is twice as small as ADE BC is half DE (the height of the guy) 1. Mirror (BC) should be at least half of the guy’s height (DE) 2. Its bottom should 1/2 of the height of guy’s eyes from the ground ‘Mirror image’ Mirror image of left hand is a right hand Inversion: converting right-handed coordinate system into left-handed one Even number of mirrors can be used to avoid inversion Applications: steering light DLP projection TV reflex camera (SLR) http://www.plus-america.com/papers.html Atomic force microscope Parabolic aspherical mirror V Make a mirror that will converge plane waves into a point Fermat’s principle: OPL W1A1 A1F W2 A2 A2F Application: headlights, W A A D W A A D 1 1 1 1 2 2 2 2 flashlights, A F A D A F A D radars, 1 1 1 2 2 2 dish antenna, In general: AF AD ….
    [Show full text]
  • 8/29/2016 1 PHYS 450 Fall Semester 2016 Lecture 02: Light Rays, The
    8/29/2016 PHYS 450 Fall semester 2016 Lecture 02: Light Rays, the Reflection of Light and Mirrors Ron Reifenberger Birck Nanotechnology Center Purdue University Lecture 02 1 Mirrors - Historical Context One of the oldest commonly observed optical phenomena is reflection. Reflection: mirrors . water mirrors: surface of lake eons ago . obsidian (volcanic glass) about 6,000 B.C. in Anatolia . from polished copper in Mesopotamia and Egypt around 4000 to 3000 B.C. looking glasses discovered in Egyptian pyramids built circa 1900 BC. Reflection is the change in direction of a wavefront at an interface between two different media. Initial understanding built on empirical observations. Early Chinese, Greek, and Arabian philosophers develop the science of geometrical optics - a method of studying light as rays instead of waves (or particles). 2 1 8/29/2016 Interaction of light with matter visible IR I=Irradiance (Intensity) A T R I (W/m2) = R + T + A (conservation of energy) . Aluminum: Good reflectivity throughout optical and near-IR. Inexpensive. Three regimes: . Silver: Better reflectivity than Al if > 500 nm, but degrades under ambient •if RI, mirrors conditions (tarnishes) and dies in the blue. •if AI, filters and absorbers . Gold: Better reflectivity in the IR, but not so good in the optical. •if TI, lenses 3 Specular vs. diffuse reflection Specular Collimated Reflection light beam Smooth surface: specular reflection Collimated Diffuse light beam Reflection Rough surface: diffuse reflection 4 2 8/29/2016 Reflection of Light When viewed from above, light from a laser pointer reflects from a vertical mirror. Definitions . Incident light: the light striking the mirror .
    [Show full text]
  • Reflection of Light with Two Plane Mirrors—Double Mirrors Placed at a 90-Degree Angle
    Level: Grades (K–4), (5-8) Activity: 2 Reflection of Light With Two Plane Mirrors—Double Mirrors Placed at a 90-Degree Angle Objective Theory B Reflection A The student will experiment with When you place two plane mirrors reflections of two plane mirrors placed at a 90-degree angle, the image of the at a 90-degree angle to see what will first mirror is reflected in the second be reflected. mirror so that the reversed mirror image is reversed again, and you see a true image. (See Glossary, page 73.) The Science and Mathematics Standards placement of images in the mirror will vary with the distance of the person or object in front of the mirror. Science Standards Science as Inquiry Materials Physical Science Mathematics Standards Problem Solving • 1 protractor Communication • 2 plane mirror tiles 12 inches square Connection (These mirrors should be backed Computation/Estimation with heavy cardboard and sealed Measurement around the edges with thick tape. The mirrors should then be taped together to form two to four hinges. You now have framed mirrors that can stand alone.) • cardboard • tape Optics: An Educator’s Guide With Activities in Science and Mathematics EG-2000-10-64-MSFC 17 Procedures Observations, Data, and Conclusions AB CD 1. Place the mirrors at a 90-degree angle. 1. What did you observe during this activity? 2. Place yourself in front of the mirrors. 2. What information did your eyes 3. Look into the mirror and follow the give you? instructions. All instructions should be followed while looking into the 3.
    [Show full text]
  • Plane Mirror •A Plane Mirror Is a Flat Mirror That Reflects Light Specularly
    General Physics II Ray Optics 1 Waves and Wavefronts •From a point source, spherical waves emanate outward. All points on a sphere concentric with the source are in phase (same point in oscillation cycle: crest, trough, etc.). Such a sphere is called a wavefront. Electron waves (IBM Almaden) 2 Rays • The direction of the outward radiating waves is along radial lines emanating outward from the source. These lines are perpendicular everywhere to the wavefronts and are called rays. • At very large distances from the source, the wavefronts have very large radii and are essentially flat planes. The rays are then (nearly) parallel lines. • It is sometimes convenient to analyze the behavior of light in terms of the ray model. In this model, light travels in straight lines (i.e., rays) from a source. 3 Seeing Objects • To see an object, light rays from it must enter your eye. You see a self-luminous object like a flame because light rays emitted by it enter your eye (and is then processed by your brain). • To see a non-luminous object, light rays must be reflected from it and then enter your eye. • The sky appears bright in the daytime because sunlight is scattered in all directions by atoms in the atmosphere. Some of this scattered light enters your eye, which allows you to see the bright sky, even though the particles themselves are not visible. 4 Workbook: Chapter 18, Question 1 5 Reflection • When light is reflected from a smooth flat surface, a parallel bundle of rays, or, parallel beam, that is incident on the surface is reflected as a parallel beam.
    [Show full text]