![]() ![]() Although both are waves, light exhibits particle nature too. There are several dissimilarities between light and sound. A change in frequency of sound waves creates an audible sensation ( a difference in pitch) and a change in the frequency of light wave causes a visual sensation (a difference in color). Frequency or wavelength affects both of them. While propagating at the interface of two media, both light and sound suffer loss of speed, change in direction or get absorbed. Both undergo refraction, diffraction and interference. Light and sound both are waves, but sound requires a material medium to travel, and hence cannot travel in empty space while light can travel through vacuum but not through opaque materials. Speed of sound depends on the ratio of density and pressure of the medium and also the temperature. It is the properties of sound waves that characterize sound namely frequency, wavelength, amplitude, speed and etc. Through gases, liquids and plasmas sound can be transmitted as longitudinal waves, while through solids, it can be transmitted as both longitudinal and transverse waves. Sound is composed of longitudinal waves (also called compression waves), that is, alternate compressions and expansions of matter parallel to the direction of wave. Presence of atoms, molecules or some structure is necessary for sound to travel it corresponds to the propagation of a disturbance through a medium. Sound can be interpreted as mechanical vibrations that travels through all forms of matter : gases, liquids, solids and plasmas. Intensity, frequency or wavelength, direction and polarization are some of the primary properties of light. Light can be emitted and absorbed as tiny energy packets named “photons”. Apart from being a wave, light exhibits properties of particles. ![]() Light travels through air and vacuum at an speed of around 3 x (10) 8 ms -1. In empty space, where there is no substructure, the speed of light is independent of wave frequency. Light travels as transverse waves transverse to the direction of propagation. Light is the most familiar form of electromagnetic waves. Light falls into the category of electromagnetic waves, while sound is a mechanical wave. Light triggers the sensation of seeing and sound stimulates the hearing. When looking through double slits, it is impossible to see only the double‐slit pattern because the double‐slit is really two single slits therefore, the actual observed pattern is that of superimposed double – and single‐slit patterns.Light and sound play a vital role in human life. Position of fringes produced by single-slit diffraction. The center region of the pattern will be the brightest band because the wavelets completely, constructively interfere in the middle. The positions of the light and dark fringes formed by a single slit are summarized in the intensity versus angle sketch shown in Figure 3. ![]() Again, the waves through two regions cancel in pairs, but now the waves from one region constructively interfere to produce a bright point on the screen. The region of wavelets is divided into three. Whenever the path difference between AP and CP is a whole number of wavelengths, a dark fringe will be produced on the screen because the wavelets can be seen to completely cancel in pairs.įigure 2 illustrates the light rays traveling to another point on the screen. Where λ is the wavelength and w is the slit width. Applying the definition for sine to the figure yields ![]() The triangle ACD is nearly a right triangle if P is quite distant. The wavelets cancel in pairs thus, point P is a minimum or dark point on the screen. Also for every wave originating between A and B, there is another point between B and C with a wavelet that will destructively interfere. As shown, AP exceeds BP by half a wavelength therefore, the represented waves destructively interfere. The rays from A and B interfere at P on a distant screen. Figure 1 shows the wave‐ray diagram used to analyze the single slit.ĭiffraction of light through a single slit. Imagine that the slit is wide enough to allow a number of wavelets. The difference is that sound waves are long while light waves are extremely short because differentiation is proportional to wave length it is not easy to observe the bending of light when it passes through a small aperture or goes around a sharp edge.Ī single slit yields an interference pattern due to diffraction and interference. In contrast, diffraction is quite difficult to observe with light. It is not at all remarkable to hear sound through an open door or even around corners. The diffraction of sound is quite obvious. Diffraction is the effect of a wave spreading as it passes through an opening or goes around an object. Thomas Young's double‐slit experiment shows that light spreads out in wavefronts that can interfere with each other. ![]()
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