A) When the person looks at different objects through the hot air over fire the objects appear to him to be moving or shaking slight because of the refraction of the light. The air density is the reason for the refraction of the light. The air density is different from the two places hence the refraction causes the light shaking of the objects. the air density would also be a good reason for this kind of situations.
B) When white light passes through a triangular glass prism, a student observes that different colors bend through different angles with respect to the incident white light because of the phenomena is dispersion of light and different angles is because of different wavelength of components of the color of white light. this phenomena can be observed a lot in our day to day normal situations when we come across the glass prism.