PASCO OS-8500 INTRODUCTORY OPTICS SYSTEM - Manual (Page 64)

Introductory Optics System 012-02744K
®
58
Exp 9: Two-Slit Interference
Suggestions on – Procedure
Actual values obtained will vary due to differences in
eyesight, but they should at least be ordered with red
longest and blue shortest.
Answers to – Questions
➀
Here AP and BP are drawn parallel to each other.
color n AB (mm) X (mm) L (mm) wavelength (m) average (m)
red 1 0.125 3 450 833e—9 725e—9
2 0.125 5 450 694e—9
3 0.125 7 450 648e—9
green 1 0.125 2 450 555e—9 555e—9
2 0.125 4 450 555e—9
3 0.125 6 450 555e—9
blue 1 0.125 2 450 555e—9 501e—9
2 0.125 3.5 450 486e—9
3 0.125 5 450 462e—9
➁
a’ +
θ’ = 90°
a +
θ = 90°
a = a’, since the center line is parallel to AP.
therefore,
θ = θ’
a'
a
θ
θ '
B
A
P
P
AB
n
sin tan
–1 X
L
=
λ
sin tan
–1 X
L
=
λ n
AB
but if then
(unless n = 0)
However, sin(x) - 1, so the equation is not valid
unless n = 0. Therefore you would expect to see
only the zeroth maxima.
λ n
AB
> 1