Answer:
h=18.05 cm
Explanation:
Given that
m= 25 kg
K= 1300 N/m
x=26.4 cm
θ= 19.5 ∘
When the block just leave the spring then the speed of block = v m/s
From energy conservation



By putting the values


v=1.9 m/s
When block reach at the maximum height(h) position then the final speed of the block will be zero.
We know that

By putting the values

h=0.1805 m
h=18.05 cm
You need to use Planck's law:
E = h·υ = (h·c)/λ
Without making all the calculations, a fraction is bigger than another when the denominator is smaller. Therefore you need to find the smallest wavelength (λ) which is 450nm.
You could also be helped by colors: in order of decreasing energy, you have blue - green - yellow - red.
In any case, the correct answer is a).