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1 3.0×10 8 656×10−9=2.0×10 8 λ⇒λ=437 nm.

2 a1.0 s

b

3

4For red light because red has larger wavelength.

5The third order maximum is expected at an angle given by sin θ=3 λ d or approximately θ≈3 λ d since angles are small. The first minimum of the single slit pattern is at θ≈λ b=λ(d 3)=3 λ d, i.e. at the same angle and so the intensity there is zero.

6From d sin θ = n λ we find n × 400 = m × 500. The smallest integers satisfying this equation are n = 5, m = 4.