Under many circumstances, light exhibits the same behavior as sound or water waves. These objects are much larger than the wavelength of light, so the analysis can be done using geometrical optics, a simple model that uses rays and wave fronts. Interference in light waves is not easy to observe because the wavelengths are so short. This curriculum was originally developed for a seniorlevel optics course in the department of physics and astronomy at brigham young university. Derive the formula that relates the wavelength of the light to the interference pattern fringe spacing. Another distinguishing aspect of light sources is the distribution of wavelengths present. Optics is a branch of physics that deals with the determination of behaviour and the properties of light, along with its interactions with the matter and also with the instruments which are used to detect it. In this video i will show you how to find the intensity of double source interference pat. When we discussed the reflection and refraction of light, light was interacting with mirrors and lenses. Because light is a wave, the superposition principle is valid to determine the constructive and destructive interferences for light waves. Diffraction and interference light thin film interference. In order to form an interference pattern, the incident light must satisfy two conditions. W e now learn how treating light as waves rather than as rays leads to a satisfying description of such phenomena.
According to wave theory of light, the light is a form of energy which travels through a medium in the form of transverse wave motion. In physics, interference is a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude. Thomas young first demonstrated interference in light waves from two sources in 1801. There are certain things that only waves can do, for example interfere. Interference of light examples physics theories laws. Thomas young tried the experiment in the early 1800s, and found the expected pattern. Each slit acts like a pointsource by huygens principle. Monochromatic sources produce fringes at angles according to \dsin. Engineering physics unit iphysical optics sv college of engineering, kadapa dr. Interference of light waves and youngs experiment emedicalprep. Light waves and similar wave propagation, when superimposed, will add their crests if they meet in the same phase the waves are both increasing or both decreasing. Suppose you pass light from a hene laser through two slits separated by 0. Wave interference is the phenomenon that occurs when two waves meet while traveling along the same medium. To understand how to determine the interference conditions for double slit interference 3.
Light the physical cause, with the help of which our eyes experience the sensation of vision, is known as light or the form of energy, which excites our retina and produce the sensation of vision, is known as light. A monochromatic source, like a laser, will emit light of one specific wavelength. Constructive and destructive interference result from the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. An incandescent bulb will emit light with many different wavelengths i. The reason for this was that they werent looking at the proper scale. Voiceover youngs double slit experiment looked a little something like this.
Youngs double slit introduction light waves physics. Interference effects are harder to observe with polychromatic light. Define constructive interference for a double slit and destructive interference for a. We can see interference in action if we shine laser light through two slits onto a screen. Wave optics describes the connection between waves and rays of light. For the formation of interference pattern, two coherent light sources are required. Propagation, interference and diffraction of waves.
Topics are addressed froma physics perspective and include the propagation of light in matter, reflection and transmission at boundaries, polarization effects, dispersion, coherence, ray optics and imaging, diffraction, and the quantumnature of light. So what happens here is that he has interfered you with what you were doing. Light waves and similar wave propagation, when superimposed, will add their crests if they meet in the same phase the waves are. Jan 22, 2020 free pdf download of cbse physics multiple choice questions for class 12 with answers chapter 10 wave optics. In optical region, light has a wavelength of about half a micrometre. Interference fringe, a bright or dark band caused by beams of light that are in phase or out of phase with one another. Geometrical optics, studied in the first year, ignored the wave nature of light and so, in this. Thin film interference occurs when light waves reflecting off the top and bottom surfaces of a thin film interfere with one another. This idea that light travels through space along straight lines, although not strictly correct, is the basis of the very useful ray model of light, which explains a great deal about how we see things. According to wave theory of light, the light is a form of energy which travels through a medium in the form of. The light waves emerging from the two slits then interfere and form an interference pattern on the viewing screen. The elements of the ray theory, called geometrical optics, will be explored in. As most commonly used, the term interference usually refers to the interaction of waves which are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency.
Physics mcqs for class 12 chapter wise with answers pdf download was prepared based on latest exam pattern. Let us now study about something called as an interference of light waves. Most people observe some type of optical interference every day, but do not realize what is occurring to produce this phenomenon. Fringes width in interference of light is equal while in the diffraction of light fringes width is not. Youngs double slit introduction video khan academy. The bright bands fringes correspond to interference maxima, and the dark band interference. Some slides were adopted from phy106 particle physics module at syracuse university by dr. The properties of prisms, mirrors, and lenses are best understood in terms of light rays.
Despite descartes adoption of the wave interpretation of light. Include a picture of your interference pattern as it appears on the screen. To understand the meaning of constructive and destructive interference 2. Newton believed that light consists of particles corpuscles. It explained the laws of reflection and refraction of light at an interface. The study of light as a wave is called wave optics. We give a heuristic discussion of the physics, and generalize it to get the fundamental result of fourier optics. The physics of light and color interference olympus. Diffraction and interference light problems the physics. Physics mcqs for class 12 with answers chapter 10 wave optics. The narrow slits s 1 and s 2 act as sources of waves. Interference of light waves is defined as the modification in the distribution of light energy when two or more waves superimpose each other. The interference of waves causes the medium to take on a shape that results from the net effect of the two individual waves upon the particles of the medium.
The text is designed for upperlevel undergraduate students with a physics background. It begins with explaining ideas of superposition of harmonic oscillations leading to. Wave optics interference of light waves and youngs experiment. Optics the branch of physics consisting properties of light. Topics covered include re ection and transmission at boundaries, dispersion, polarization e ects, di raction, coherence, ray optics and imaging, the propagation of light in matter, and the quantum nature of light. Ray optics is based on rectilinear propagation of light, and deals with mirrors, lenses, reflection, refraction, etc. Ap physics interference in the 18century, physicists discovered that waves displayed interference patterns. Young was the english physicist who first did an experiment of this kind. To understand how to determine the intensity of the light associated with double slit. This is because the regular lightdark bands are superimposed on the light pattern from the single slit.
Then you come to the chapter on wave optics, and you are told that light travels as a wave, that it can bend around objects, it can diffract and interfere, etc. Interference of light when two light waves of similar frequency having a zero or constant phase difference. In other words, t he amplitude of the diffraction pattern modulates the interference pattern. Free pdf download of cbse physics multiple choice questions for class 12 with answers chapter 10 wave optics. What is difference between interference and diffraction. Note that the observed laws of geometric optics follow from the assumption that light is a wave. If light is a wave, two sources emitting waves in a synchronized fashion1 should produce a pattern of alternating bright and dark bands on a screen. Students can solve ncert class 12 physics wave optics mcqs pdf with answers to know their preparation level.
An important characteristic of light waves is their ability, under certain circumstances, to interfere with one another. Light emitted from an incandescent lightbulb is incoherent because the light consists o. The explanation for this requires the concept of interference, which we shall shortly encounter. The branch of optics that considers the behavior of light when it exhibits wave characteristics. The controversy between newton and huygens about the nature of light was settled in 1801 when young demonstrated convincingly that light shows all the characteristic of waves. In physics, interference is the addition superposition of two or more waves that result in a new wave pattern. Youve got a barrier with two holes in it, but these holes are so small and so close together we characterize them as slits, and double because theres two of them. The corpuscular model predicted that if the ray of light on refraction bends towards the normal then the speed of light would be. Because both the sodium lamps are not coherent pairs of light sources. Topics are addressed froma physics perspective and include the propagation of light in matter, reflection and transmission at boundaries, polarization effects, dispersion.
Physics interference of light 1 of 8 path and phase. Suppose you are busy studying in your room and one of your friends calls you out for cricket. Geometrical optics where light is described by rays which show the paths of energy transfer. Interference of light, waves from alevel physics tutor.
This type of interference is the reason that thin films, such as oil or soap bubbles, form colorful patterns. Mar, 2020 the interference is the combination of superposition of two or more waves that are in a point of space. It is said that interference occurs when a peak of the light wave meets a trough and the wave cancels to zero, giving a dark band on the screen. When two or more light waves having the same frequency, same wavelength and same amplitude meet together in a medium at a point, they cancel or enhance the effect of each other at that point. Physical optics lecture notes pdf 44p this note covers the following topics. Diffraction huygens principle huygens principle 1 each point on a wave front is the source of a spherical wavelet that spreads out at the wave speed. Suppose if the crest of one wave falls on the trough of another wave, then the amplitude here is minimum.
The diffraction is the deviation suffering waves around the edges and corners that occurs when a portion of a wavefront is interrupted or cut it by a barrier or obstacle. These sources should emit continuous waves of same wave length and same time period. Intensity in interference and diffraction pdf download book. Intensity in interference and diffraction pdf download.
Since b is 180 out of phase with a, the two signals always interfere destructively at the position of a. One of the reasons that newton thought that light was a stream of particles was that light did not, apparently, display interference patterns. The interference is the combination of superposition of two or more waves that are in a point of space. The elements of the ray theory, called geometrical optics, will be explored in chapters l2 and l3.
We now learn how treating light as waves rather than as rays leads. In our discussions of geometric optics we completely ignored the fact that light can also behave as. The speed of light in a medium depends upon the nature of medium. In order to observe interference in light waves, the following conditions must be met. Optics, in a simple manner, is used to describe the behaviour of visible light, infrared light, and the ultraviolet. We begin by discussing interference from a double slit. A light source emits visible light of two wavelengths. Interference is the process in which two waves combine together and the resultant wave may have a greater or smaller amplitude. Here the waves do not have the same displacement and the waves are out of phase.
These phenomena cannot be adequately explained with the ray optics used in chapters 35 and 36. The size of an adults pupil is discussed in physics of the eye. The intensity pattern is in effect a combination of both the singleslit diffraction pattern and the double slit interference pattern. However, if light waves are bands or shells of high densities of photons interspersed with bands of zero photons, then how can this be. Physics notes for class 12 chapter 10 wave optics wave optics describes the connection between waves and rays of light. Light is a form of energy which generally gives the sensation of sight. For interference the waves emitted by sources should be with zero phase difference or no phase difference. This approximation is good for the study of interference. The waves emerging from the slits originate from the same wave front and therefore are always in phase. From physical science study committee, college physics, lexington, ma, heath, 1968. Two source interference, double slit interference, coherence, intensity in double slit interference using phasor method, interference from thin films, newtons rings, diffraction and wave theory of light, singleslit diffraction, intensity in singleslit diffraction using phasor.