Magine a thin layer of water (n = 1.33) spread across a block of ice (n = 1.309). (a) if rays of light are directed downwards and reflect/refract with respect to the thin layer of water, determine the minimum water thickness that produces the least reflection at a wavelength of 550 nm. (b) suppose a flashlight was turned on and frozen in the block of ice pointing upwards, determine the minimum water thickness that produces the most reflection at a wavelength of 650 nm.

Part a)

Part b)

Explanation:

Part a)

As we know that when light incident on the water layer then for least reflection of light then path difference of two reflected light is equal to the odd multiple of half of wavelength of light

so here we have

Part b)

As we know that when light incident on the water layer then for maximum reflection of light then path difference of two reflected light is equal to the integral multiple of wavelength of light

so here we have

d.7.5cm is your answer