Yes! The probability density is:

The value of y^{2} is a maximum
when sin npx/l is a maximum. The maximum of
any sine is 1, so:y^{ 2}_{max}
= 2/l

The length of the retinal p-chain, which
has 12 atoms is:

(a) 11X0.15 = 1.65 nm, or

(b) 12X0.15 = 1.80 nm