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Diffraction

1) Heliumneon laser light (= 632.8 nm) is sent through a 0.300-mm-wide single slit. What

is the width of the central maximum on a screen 1.00 m from the slit?

Central maximum, m=1

2y=4.22m

2) Light of wavelength 587.5 nm illuminates a single slit 0.750 mm in width. (a) At what

distance from the slit should a screen be located if the first minimum in the diffraction

pattern is to be 0.850 mm from the center of the principal maximum? (b) What is the

width of the central maximum?

(a) Sin= y/ L=m /a

Therefore, for first minimum, m = 1 and

(b) =2y1y1 = 0.850 mm

w = 2(0.850 10-3) = 1.70 mm

3) A circular radar antenna on a Coast Guard ship has a diameter of 2.10 m and radiates at a

frequency of 15.0 GHz. Two small boats are located 9.00 km away from the ship. How

close together could the boats be and still be detected as two objects?

(1)

The wavelength of 15 GHz=15x109Hz is c/f=0.02m

From (1) d=105 meter.

4) A heliumneon laser (you know its )is used to calibrate a diffraction grating. If the first-

order maximum occurs at 20.5, what is the spacing between adjacent grooves in the

grating?

Sin=0.35

Line spacing=> d=/sin=632.8nm/0.35=1.81x103nm=1.81 m

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