Answer the following questions: (a) In a single slit diffraction experiment, the width of the slit ismade double the original width. How does this affect the sizeand intensity of the central diffraction band? (b) In what way is diffraction from each slit related to theinterference pattern in a double-slit experiment? (c) When a tiny circular obstacle is placed in the path of light froma distant source, a bright spot is seen at the centre of the shadowof the obstacle. Explain why? (d) Two students are separated by a 7 m partition wall in a room10 m high. If both light and sound waves can bend around obstacles, how is it that the students are unable to see eachother even though they can converse easily. (e) Ray optics is based on the assumption that light travels in astraight line. Diffraction effects (observed when light propagatesthrough small apertures/slits or around small obstacles)disprove this assumption. Yet the ray optics assumption is socommonly used in understanding location and several otherproperties of images in optical instruments. What is the justification?
(a)
Increasing the width of the slit will decrease the size of the central diffraction band. If the width of slit is twice the original width, then the size of the central diffraction band reduces to half of the original. This increase the central intensity upto four times.
(b)
In a double-slit experiment the interference pattern each slit is modulated by diffraction pattern. Thus, the pattern is the result of the interference of diffracted wave from each slit.
(c)
The bright spot observed when a tiny circular obstacle is placed in the path of light from a distant source, at the centre of the shadow of obstacle. This is due to refraction of light from the edge of circular obstacle which constructively hits at center of shadow. This constructive interference produces a bright spot.
(d)
The deflection of the wave’s at large angle is possible when the size of obstacle is comparable to wavelength of waves. In this case the wavelength of the object is too small in comparison to the obstacle that students are unable to see each other.
However the wavelength of sound waves is comparable to the wall. Thus, the bending takes place at the large angles in case of sound waves. Thus, students are able to hear each other.
(e)
The size of aperture is much larger than the wavelength of light,
(a)
Increasing the width of the slit will decrease the size of the central diffraction band. If the width of slit is twice the original width, then the size of the central diffraction band reduces to half of the original. This increase the central intensity upto four times.
(b)
In a double-slit experiment the interference pattern each slit is modulated by diffraction pattern. Thus, the pattern is the result of the interference of diffracted wave from each slit.
(c)
The bright spot observed when a tiny circular obstacle is placed in the path of light from a distant source, at the centre of the shadow of obstacle. This is due to refraction of light from the edge of circular obstacle which constructively hits at center of shadow. This constructive interference produces a bright spot.
(d)
The deflection of the wave’s at large angle is possible when the size of obstacle is comparable to wavelength of waves. In this case the wavelength of the object is too small in comparison to the obstacle that students are unable to see each other.
However the wavelength of sound waves is comparable to the wall. Thus, the bending takes place at the large angles in case of sound waves. Thus, students are able to hear each other.
(e)
The size of aperture is much larger than the wavelength of light,
