The answer is polarization. It is just like when you are on a boat and use polarized glasses so the water wont reflect into your eyes it also intensifies the color of the water so you can see better into the water.
example: you cant see any fish because glare from the sun, put on polarized glasses and now you can see fish up to 30 feet deep.
According to the Bernoulli's equation,the pressure difference between the wide and narrow ends of the pipe is given by
Here, 
is the velocity of water through wide ends of cylindrical pipe and 
is the velocity of water through narrow ends of cylindrical pipe.
Given, 
Now from equation continuity,
.
Here, 
and 
are cross- sectional areas of wide and narrow ends of cylindrical pipe.
As pipe is circular, so
.
At the second point, the diameter is halved, which means the radius is also halved. Therefore,
Substituting these values with the density of water is 
in pressure difference formula we get.
Answer:
v=wavelength ×f
wavelength=v/f=455/655=0.694m
