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Essential idea: Single-slit diffraction occurs when a wave is incident upon a slit of approximately the same size as the wavelength.
Nature of science:
Development of theories: When light passes through an aperture the summation of all parts of the wave leads to an intensity pattern that is far removed from the geometrical shadow that simple theory predicts. (1.9)
Understandings:
The nature of single-slit diffraction
Applications and skills:
Describing the effect of slit width on the diffraction pattern
Determining the position of first interference minimum
Qualitatively describing single-slit diffraction patterns produced from white light and from a range of monochromatic light frequencies
Guidance:
Only rectangular slits need to be considered
Diffraction around an object (rather than through a slit) does not need to be considered in this sub-topic (see Physics sub-topic 4.4)
Students will be expected to be aware of the approximate ratios of successive intensity maxima for single-slit interference patterns
Calculations will be limited to a determination of the position of the first minimum for single-slit interference patterns using the approximation equation
Data booklet reference:
Where:
θ = angle of diffraction [rads]
λ = wavelength of light [m]
b = aperture width [m]
Small Angle Approximation (rads)
Monochromatic light with a wavelength of 400 nm passes through a single slit and falls on a screen 90 cm away. If the distance of the first-order dark band is 0.3 cm from the center of the pattern, what is the width of the slit?
Theory of knowledge:
Are explanations in science different from explanations in other areas of knowledge such as history?
Utilization:
X-ray diffraction is an important tool of the crystallographer and the material scientist
Aims:
Aim 2: this topic provides a body of knowledge that characterizes the way that science is subject to modification with time
Aim 6: experiments can be combined with those from sub-topics 4.4 and 9.3
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