An intern engineer is designing a set up based on diffraction to measure the dia
ID: 1385657 • Letter: A
Question
An intern engineer is designing a set up based on diffraction to measure the diameter of thin wires. He tested the setup by using a known wire of diameter 0.02 mm. He used a coherent light source of wavelength 361 nm. He positioned the viewing screen 4.8 m from the wire.
a) What is in m the position of the first diffraction minimum due to the light?
b) What is in m the width ?ycentral of the central diffraction maximum?
c) What is in m the position of the second order diffraction maximum?
d) What is in m the width ?y of the second order maximum?
Explanation / Answer
given
wvelength,lamda = 361 nm
slit width, d = 0.02 mm 2*10^-5 m
distance from slit to screen, R = 4.8 m
a) for first dark fringe, y1 = lamda*R/d
= 361*10^-9*4.8/(2*10^-5)
= 0.0866 m
b) central bright fringe width = 2*lamda*R/d
= 2*361*10^-9*4.8/(2*10^-5)
=0.1732 m
c) fr second order difraction maximum = (3/2)*lamda*R/d
= 1.5*0.0866
= 0.13 m
d) width = 0.1732/2 = 0.0866 m
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