Double-Slit&DiffractionGrating

[匿名]

2009-02-22 9:10 pm

01) Suppose a thin piece of glass is placed in front of the lower slit so that the two waves enter the slits 180 degree out of phase. Describe in detail the interference pattern on the
screen.

02)What is the highest spectral order that can be seen if a grating with 6000 lines per cm
is illuminated with 633-nm laser light? Assume normal incidence.

抱歉，這兩題我實在不會解

可以幫幫我嗎？

回答 (1)

Prof. Physics

2009-02-23 4:43 am

✔ 最佳答案

1. This is a Young double slit experiment with the two waves were in phase initially.

In this circumstance, you will have the central maximum (constructive interference in the centre), then there will be adjacent minimum and maximum seen on the screen.

If now a thin glass piece is added and the two waves are 180* out of phase, then you will see a dark fringe in the centre since destructive interference occurs there (the path difference is half wavelength), and the bright and dark fringes patterns will be interchanged correspondingly.

2. Grating separation, d = 0.01 / 6000 = 1 / 600 000 m

Wavelength, s = 633 X 10^-9 m

By ms = dsin@

m = dsin@ / s <= d / s (Since sin@ <= 1)

m <= (1 / 600 000) / (633 X 10^-9)

m <= 2.63

m is the highest integer not greater than 2.63

So, m = 2

Therefore, the highest spectral order that can be seen is 2.

參考: Physics king

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