(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

When a 450-nm light is incident normally on a certain double-slit system, the number of interference maxima within the central diffraction maxima is 5. When 900-nm light is incident on the same slit system, the number of interference maxima within the central diffraction maxima is ______?

2. Relevant equations

3. The attempt at a solution

The answer is given as 5, but I can't figure out why.

[tex]dsin\theta = m \lambda[/tex]

[tex]dsin\theta = n \lambda^{'}[/tex]

Since dsin(theta) shouldn't change,

n = (m/2)

If we have 5 bright fringes in our central envelope, m = 2, therefore n=1.

So the number of bright fringes in the new central envelope is 2n+1 = 3 which is incorrect.

What am I misunderstanding?

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# Central Diffraction Maximum Double Slit

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