I do not believe that the lake would freeze at the bottom only because of the fact that fish ( sharks mostly) live deep in the waters and it is actually warmer down there. the higher up you are, the more closer you are to the atmosphere and the climate change. Anything way under the water does not always get affect by the climate. the only thing that would affect anything for the most part underwater could be underwater volcanic eruptions and underwater earthquakes, which would essentially cause the bottom of the ocean or lake to split and become reefs.
an orange fringe at 0°, yellow fringes at ±50° and red fringes farther out.
In the visible spectrum- red to violet, red has the highest wavelength.
The maximum internsity for diffraction grating is given by,
Sinθ = mλ/d
It is concluded that the angle of diffraction increases with increase in wavelength'λ' . So, red fringe will be farthest from the center, orange light will be at the center and yellow fringe will be at 50°.
Therefore, The new pattern consists of : an orange fringe at 0°, yellow fringes at ±50° and red fringes farther out.