It is observed that smaller the width of the aperture, greater is the spreading of the waves. Diffraction of water waves in a ripple tank through a small aperture is shown in the figure. However, light having small wavelength can be diffracted only through a very sharp object such as the edge of a blade and diffracting grating. This is due to the wavelength of a sound wave is nearly equal to the dimension of doors and windows. Due to diffraction of sound through the doors and windows, a sound is heard inside the room from an outside source. It is a wave phenomenon and occurs if the wavelength of the wave is of the same order as the dimension of a diffracting obstacle. Different speeds of sound produce refraction.ĭiffraction is the phenomenon of spreading of waves around the corners of an obstacles or apertures. Due to the effect, sounds are easier to hear at night than during the day times as shown in the figure. So, sound waves then tend to bend away from the ground resulting in a sound that does not seem to travel well as shown in the figure. On a warm day, the air near the ground becomes warmer than the rest of the air and the speed of sound near the ground increases. This occurs in uneven winds or when sound is travelling through an air of uneven temperatures. Soundwave bends when the parts of wave fronts travel at different speeds. Reverberation occurs after incident rays undergo multiple reflections. Since the sound wave in speech has a wavelength of various meters, they are reflected from rough surfaces such as cliffs, walls etc. The regular reflection occurs from a surface if a whole part of an incident wavefront is reflected uniformly. This can be observed in a simple experiment in which a source of sound such as a transmitter sends sound at a certain angle to the normal to a wall and a higher sound is received from reflection at the same angle on another side of the normal. Sound waves are reflected from the surfaces like light waves, obeying laws of reflection angle of incident is equal to the angle of reflection. Reflection, Refraction, Diffraction and Interference of Sound Waves Reflection Reflection
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