Refracts, Interferes and Diffuses

Light "refracts."

When observing a straw submerged in a glass of water, the segment of the straw within the liquid seems distorted. What is the reason behind that?
Light "refracts" at the interface between air and water within the glass. Refraction transpires due to the varying velocities of light in air and water. Our eyes perceive the dispersed light from the straw submerged in the water; nevertheless, refraction transpires as the light transitions from the water to the air. Nevertheless, the light emanating from the water seems to travel directly to our eyes, leading to the formation of a "virtual image" along the line stretching from the refracted light. Consequently, the tip of the straw in the water seems to have shifted from its true location.

Light "interferes."

What is the process by which the captivating colours of soap bubbles are produced?
Light propagates in several directions, resulting in the continuous intersection of light waves. The occurrence of light waves colliding with one another is termed "interference."
When the crests of these waves coincide, the crests amplify in magnitude. When the crests and troughs of the waves intersect, they negate one another. This interference is responsible for the perception of the diverse colours in soap bubbles.
A soap bubble consists of an exceedingly thin layer. Light reflecting from the outside and interior surfaces of this film interacts, resulting in the observed colours. Furthermore, the viewing angle of the light interference in the soap bubble film varies due to the continuous motion of the soap bubble.
The oscillating light waves increase and negate one another, resulting in our perception of enigmatic and ever-shifting colours.
 

Light "diffuses"

What causes a rainbow to manifest in the sky following rainfall?
The sunlight is referred described as white light, however it is, in fact, a composite of several coloured lights that look white to the human sight. Employing a prism to disperse the white light beam enables the observation of the several colours of light.
This occurrence is referred to as the "dispersion" of light. In the natural environment, water droplets function as prisms when suspended in the atmosphere post-precipitation.
Light that impinges upon water droplets undergoes refraction and penetrates the droplet's interior, reflects internally, and refracts upon departing the droplet. The water droplets in the atmosphere function similarly to a prism, resulting in dispersion, wherein the light that reaches our eyes manifests as continuous bands of varying colours. That is the phenomenon that creates a rainbow.
Upon closer examination of the rainbow, one may occasionally observe a secondary rainbow, characterised by a reversed colour sequence, situated on the outside periphery of the primary rainbow. The secondary rainbow is produced by light that reflects twice within a water droplet before reaching our sight.