Young's Double-slit Equation Question

[ova5676]

Homework Statement

What is the maximum order number possible for red light (630 nm) illuminating a double slit with separation 3.0 x 10^5 m.

Texbook answer: 4.76 x 10^11

Homework Equations

mλ = d*sinθ
mλ = d*x/L

The Attempt at a Solution

So λ = 630 nm or 6.30 x 10^-7 m, and d = 3.0 x 10^5 m, but if you use either equation you're missing m or the angle, or x (space between bands) or L (sheet to slit distance).

I'm really confused.

 

[ehild]

What is the maximum value of sinθ? (mλ = d*x/L holds for small angles only.)

ehild

 

[Geezer]

What is the maximum value of sinθ? (mλ = d*x/L holds for small angles only.)

This ^^

Using this hint--and the equation with sin(theta)...no small angle approximations--you should have no problem getting the textbook answer.