Yes
The equation is period = 2 pi / (sqrt of (length/9.8)); so plug 3.17 in for period and solve for length
D, oscillate perp. To direction of propagation
Think it’s 3/5 so 0.6Hz
Believe it’s constructive interference
?
I think it’s the lower pitch (C)
Through 18…? I never covered optics and lenses sorry!
