Physics: Principles and Problems

Chapter 18: Refraction and Lenses



		The requirements for the sketch are: for reflection, angle in equals angle out for refraction, bend away from center
		Path of the sound wave.
		Model of reflecting and refracting sound waves in the sun.

		The daylight is extended because of refraction, not only on the equinox, but on all days. As light passes through our atmosphere, it will slow down and consequently it will bend. On the horizon, light must pass though a large portion of air, causing any celestial body to appear about half a degree higher on the horizon than it actually is. So at sunrise, we see the entire image of the sun before it physically is above our horizon.
		Exaggerated diagram of atmospheric refraction
		Mercury has no atmosphere. If Earth had no atmosphere, then there would be no refraction. Without refraction, the day and night would be equal length on the equinox. If one wanted to be picky, one could celebrate the equality of day and night on March 15th, the true day of equal night and light.