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How do you find the derivative of the diffraction grating equation, dsin0=nL? (L is lander)
1- recognise that the red triangle demonstrates the phase difference, nL
2- Recognise that the two triangle are similar, therefore theta is apart of both of them
3- use Sin0=O/H to find Sin0=nL/d
4- Rearrange to get dsin0=nL
What type of light is used during diffraction and which apparatus produces it?
Monochromatic light, produced by a laser
Why is a diffraction grating more useful than Young’s Double Slip Experiment?
A diffraction grating produces a much sharper image of the interference pattern
Are the bright fringes narrower or wider than the dark fringes?
The bright fringes are both narrower and brighter, whilst that dark fringes are wider and darker
Where there are regions of constructive interference there are also regions of…?
Maximum Intensity
How can we calculate d from N?
d=1/N, where N is the number of lines per mm (or m)
Where is theta always measured from and what does this mean for the other orders of n?
Theta is always measured from the center (n=0), this means that the value of theta increases as the number of orders increases
How do you find angular separation?
You subtract the smaller angle from the larger one. e.g. the angular separation between the first and second maxima is THETA2-THETA1
What is the maximum angle of diffraction, with which maxima can be viewed?
When the beam is at right angles to the grating. Therefore 0=90o and sin0=1
How do you calculate the highest order of maxima that is visible?
n=d/Lander
How are diffraction gratings used for optical fibers?
They are used to select the optimum wavelength of light for use in optical fibers
What is the main purpose of diffraction gratings?
They are used to separate light of varying wavelengths with high-resolution
What are some of the uses of diffraction gratings, regarding spectrometers?
(Up to 7 points)
1-Analyse light from stars
2-Analyse the composition of a star
3- Chemical analysis
4- Measurement of red shift/ rotation of stars
5-Measure the frequency and or wavelength of light from a star
6- Observe the spectra of minerals
7- Analyse the absorption/emission spectra in stars
How are diffraction gratings used in X-Ray Crystallography?
-X-Rays are directed at a thin crystal sheet, acting as a diffraction grating, producing a pattern
-The wavelength of X-Rays is similar to the spacing in the crystal atoms
-The diffraction pattern can be used to measure the ATOMIC SPACING in certain materials
How are diffraction gratings used in Monochromator’s?
1-Used to specifically analyse a wavelength emitted by molecules in diseased cells from a biopsy sample
2- Used to help excite molecules in a sample with a specific wavelength of light
Note 
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