light

[logistic_guy]

At what angle will $\displaystyle 440$-$\displaystyle \text{nm}$ light produce a third-order maximum when falling on a grating whose slits are $\displaystyle 1.35 \times 10^{-3} \ \text{cm}$ apart?

 

[khansaheb]

At what angle will $\displaystyle 440$-$\displaystyle \text{nm}$ light produce a third-order maximum when falling on a grating whose slits are $\displaystyle 1.35 \times 10^{-3} \ \text{cm}$ apart?

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[logistic_guy]

We use the diffraction maxima formula.

$\displaystyle d\sin \theta = m\lambda$

Third-order means $\displaystyle m = 3$, then

$\displaystyle 1.35 \times 10^{-5}\sin \theta = 3(440 \times 10^{-9})$

This gives:

$\displaystyle \sin\theta = 0.0977778$

$\displaystyle \theta = \sin^{-1} 0.0977778 = 5.61^{\circ}$