Properties of Electromagnetic Waves & Light: Reflection, Refraction, & Materials, Exams of Advanced Education

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PHYS 1260 Exam 3 Questions with 100% Correct Answers | Verified | Latest Update electromagnetic waves - Correct Answer-- light is the only thing we can see * originates from the accelerated motion of electrons * electromagnetic phenomenon - electromagnetic wave: made up of vibrating electric and magnetic fields if an electron vibrates up and down 1000 times each second, it generates an electromagnetic wave w/ a - Correct Answer- frequency of 1000 Hz electromagnetic spectrum - Correct Answer-- classification of electromagnetic eaves according to frequency - lowest frequency of visible light we can see appears red - highest frequency of visible light we can see appears violet - higher frequency of light is ultraviolet -> more energetic and causes sunburns - beyond are x-ray and gamma ray - no sharp boundary b/w regions the electromagnetic spectrum spans waves ranging from lowest to highest frequencies. the smallest portion of the electromagnetic spectrum is that of - Correct Answer-visible light which of these is fundamentally different from the others? A. Sound waves B. light waves C. radio waves D. x-rays - Correct Answer-Sound waves -> all are electromagnetic waves except sound which is a mechanical wave transparent materials - Correct Answer-- light is transmitted similarly to sound * both are vibrations due to a vibrating source - how light penetrates transparent material such as glass: * electrons or molecules in the glass are forced into vibration * energy is momentarily absorbed and vibrates the electrons in the glass * when we stand in the sunlight, some of the light is stopped while other rays continue in a straight-line path * we cast a shadow = a region where light rays do not reach - either a large, far-away light source or a small nearby light source will produce a sharp shadow - a large, nearby light source produces a somewhat blurry shadow - there is usually a dark part on the inside and a lighter part around the edges of a shadow * a total shadow = umbra * partial shadow = penumbra * a penumbra appears where some of the light is blocked but where other light fills it in * a penumbra also occurs where light from a broad source is only partially blocked eclipses - Correct Answer-- solar eclipse = bc of the large size of the sun, the rays taper to provide an umbra (total eclipse) and a surrounding penumbra (partial eclipse) - lunar eclipse = the moon passes completely into the shadow of earth reflection - Correct Answer-- we say light is reflected when it is returned into the medium from which it came -> the process is *reflection* - when light illuminates a material, electrons in the atoms of the material move more energetically in response to the oscillating electric fields of the illuminating light - the energized electrons re-emit the light by which you can see the material principle of least time - Correct Answer-- the idea that light takes the quickest path going from one place to another is called *fermat's principle of least time* - see powerpoint !! law of reflection 1 - Correct Answer-- angle of incidence = angle made by the incoming ray and the perpendicular - angle of reflection = angle made by the reflected ray and the perpendicular - normal = imaginary line perpendicular to the plane of the reflecting surface; lies in the same plane as the incident and reflected rays - law of reflection = the angle of reflection equals the angle of incidence the law of reflection applies to - Correct Answer-light and sound law of reflection 2 - Correct Answer-- virtual image = is same size as object, formed behind a mirror, and located at the position where the extended reflected rays coverage; is as far behind the mirror as the object is in front of the mirror - plane mirror = note: the only axis reversed in an image is the front-back axis - shape of mirror forms a different virtual image * convex mirror (curves outward) = virtual image is smaller and closer to the mirror than the object * concave mirror (curves inward) = virtual image is larger and farther away than the object light reflecting from a smooth surface undergoes a change in: A) frequency B) speed C) wavelength D) nothing - Correct Answer-nothing * objects such as the sun seen through air are displaced bc of atmospheric refraction * atmospheric refraction is the cause or mirages when light travels from one medium to another and changes speed in doing so, we call the process - Correct Answer- refraction cause of refraction - Correct Answer-- bending of light when it passes from one medium to another - caused by change in speed of light - lenses = 2 types 1. converging (convex) lens * thicker at the center than edges * converges light 2. diverging (concave) lens * thinner at the center than edges * diverges light lenses - Correct Answer-- key features of lenses: * principle axis = line joining the centers of curvature of the 2 lens surfaces * focal point = point at which all the light rays come together * focal length = distance b/w the center of the lens and either focal point - image formation is a consequence of light traveling in straight lines - the first camera -> pinhole camera -> illustrates this fact - pinhole images are caused by small openings in leaves above - a lens nicely bends the straight-line paths of light - a converging lens can project an image the action of lenses depends mainly on - Correct Answer- refraction