Answer the following
questions:
(a) In a single slit diffraction experiment, the width of the
slit is made double the original width. How does this affect the size
and intensity of the central diffraction band?
(b) In what way is diffraction from each slit related to the
interference pattern in a double-slit experiment?
(c) When a tiny circular obstacle is placed in the path of
light from a distant source, a bright spot is seen at the centre of
the shadow of the obstacle. Explain why?
(d) Two students are separated by a 7 m partition wall in a
room 10 m high. If both light and sound waves can bend around
obstacles, how is it that the
students are unable to see each other even though they can converse
easily.
(e) Ray
optics is based on the assumption that light travels in a straight
line. Diffraction effects (observed when light propagates through
small apertures/slits or around small obstacles) disprove this
assumption. Yet the ray optics assumption is so commonly used in
understanding location and several other properties of images in
optical instruments. What is the justification?
Answer the following questions:
(a) In a single slit diffraction experiment, the width of the slit is made double the original width. How does this affect the size and intensity of the central diffraction band?
(b) In what way is diffraction from each slit related to the interference pattern in a double-slit experiment?
(c) When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of the shadow of the obstacle. Explain why?
(d) Two students are separated by a 7 m partition wall in a room 10 m high. If both light and sound waves can bend around obstacles, how is it that the students are unable to see each other even though they can converse easily.
(e) Ray optics is based on the assumption that light travels in a straight line. Diffraction effects (observed when light propagates through small apertures/slits or around small obstacles) disprove this assumption. Yet the ray optics assumption is so commonly used in understanding location and several other properties of images in optical instruments. What is the justification?
(a) In a single slit diffraction experiment, if the width of
the slit is made double the original width, then the size of the
central diffraction band reduces to half and the intensity of the
central diffraction band increases up to four times.
(b) The interference pattern in a double-slit experiment is
modulated by diffraction from each slit. The pattern is the result of
the interference of the diffracted wave from each slit.
(c) When a tiny circular obstacle is placed in the path of
light from a distant source, a bright spot is seen at the centre of
the shadow of the obstacle. This is because light waves are
diffracted from the edge of the circular obstacle, which interferes
constructively at the centre of the shadow. This constructive
interference produces a bright spot.
(d) Bending of waves by obstacles by a large angle is possible
when the size of the obstacle is comparable to the wavelength of the
waves.
On
the one hand, the wavelength of the light waves is too small in
comparison to the size of the obstacle. Thus, the diffraction angle
will be very small. Hence, the students are unable to see each other.
On the other hand, the size of the wall is comparable to the
wavelength of the sound waves. Thus, the bending of the waves takes
place at a large angle. Hence, the students are able to hear each
other.
(e) The justification is that in ordinary optical instruments,
the size of the aperture involved is much larger than the wavelength
of the light used.
(a) In a single slit diffraction experiment, if the width of the slit is made double the original width, then the size of the central diffraction band reduces to half and the intensity of the central diffraction band increases up to four times.
(b) The interference pattern in a double-slit experiment is modulated by diffraction from each slit. The pattern is the result of the interference of the diffracted wave from each slit.
(c) When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of the shadow of the obstacle. This is because light waves are diffracted from the edge of the circular obstacle, which interferes constructively at the centre of the shadow. This constructive interference produces a bright spot.
(d) Bending of waves by obstacles by a large angle is possible when the size of the obstacle is comparable to the wavelength of the waves.
On the one hand, the wavelength of the light waves is too small in comparison to the size of the obstacle. Thus, the diffraction angle will be very small. Hence, the students are unable to see each other. On the other hand, the size of the wall is comparable to the wavelength of the sound waves. Thus, the bending of the waves takes place at a large angle. Hence, the students are able to hear each other.
(e) The justification is that in ordinary optical instruments, the size of the aperture involved is much larger than the wavelength of the light used.
