Rate of Change of Diffraction Pattern with Increasing Distance Between Slits

[phyvamp]

Homework Statement

Monochromatic electromagnetic radiation of wavelength λ nm falls on double slits, creating a diffraction pattern on a screen L m away, Suppose now that the distance between the slits begins to increase at a constant rate:

dd/dt = x μm/s.

Assume that everything else remains unchanged. Find the rate at which the distance between the central maximum and first maximum is changing, in cm/s, at the instant the distance between the slits is d μm

Homework Equations

x = nλL/d

3. The Attempt at a Solution
x = λL/d
dx/dt = (λL/d) * (1/ dd/dt) is this right? I am confused about dd/dt part.

 

[J Hann]

I think you want d (1/d) / dt.