Range of wavelength from white light through a diffraction grating

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Homework Statement

A narrow beam of collimated white light falls at normal incidence upon a transmission grating with 3150 lines per cm. A spectrum is formed by the grating on a screen 30 cm away. If a 1 cm square hole is cut in the screen its inner edge being 5 cm from the zeroth order, what range of visible wavelengths passes through the hole?

Homework Equations

N$$\lambda$$ = dsin$$\theta$$

The Attempt at a Solution

$$\frac{\Delta\lambda}{\theta\Delta}$$ = $$\frac{d}{N}$$$$\sqrt{1 - sin^2\theta}$$

 

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What is the range of angle determined by the square hole ?

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