1. The diffraction relation perdicts the thinner the diffracting object, the (pi
ID: 1456094 • Letter: 1
Question
1. The diffraction relation perdicts the thinner the diffracting object, the (pick one) narrower/wider is the central diffraction peak.
2. Name some instances when you have observed diffraction outside of the lab setting.
3. Horsehair is much thicker than human hair. Do you expect the diffraction peak for a strand of horsehair to be wider or narrower than that from a human hair?
4. The central peak in a diffraction pattern is much more intense than the next order maxima. Use the plot in Fig. 15-1 to estimate the ratio of intensities.
5. How thin would your hair have to be in order for the central diffraction maximum to span +- 45 degrees on either side of the centerline? Assume red laser light wih wavelength =650 nm.
Explanation / Answer
1) wider is the central diffraction peak.
2) The closely spaced tracks on a CD or DVD act as a diffraction grating to form the rainbow pattern seen when looking at a disk.
3) Diffraction peak for a strand of horsehair is narrower than that from a human hair .
4) I = I0(sin /)2
where, = a sin / and, a sin = (2n+1)/2
=> I = I0(sin ((2n+1)/2) /(2n+1)/2))2
=> central maxima = I0 *(2/)2
=> Ist order maxima = I0 *(2/3)2
5) Here, sin45 = 1.22 * 650 * 10-9/D
=> D = 1.121 * 10-6 m
= 1.121 micrometer ---------------> thickness of hair
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