Answer:

Explanation:
Given:
mass of the boat, 
uniform speed of the boat, 
rate of accumulation of water mass in the boat, 
time of observation, 
The mass of the boat after the observed time:



<u>Now using the conservation of momentum:</u>



It will take "Exact 75 years", 'cause light takes 1 year for 1 light years.
Hope this helps!
Answer:
λ = 3.62 x 10⁻⁷ m = 362 nm
Explanation:
The grating equation gives the relationship between the wavelength, the diffraction line order and the diffraction angle. The grating equation is written as follows:
mλ = d Sinθ
where,
m = order of diffraction = 6
λ = longest wavelength = ?
d = 1/(460 rulings/mm)(1000 mm /1 m) = 2.17 x 10⁻⁶ m/ruling
θ = Diffraction angle = 90° (for longest wavelength)
(6)λ = (2.17 x 10⁻⁶ m/ruling) Sin 90°
λ = (2.17 x 10⁻⁶ m/rulings)/6
<u>λ = 3.62 x 10⁻⁷ m = 362 nm</u>