Refraction. Some phenomenon related to refraction of light. Twinkling of stars. Why do twinkle stars. Atmospheric refraction. Delayed sunset. Actual and apparent positions. Sun is visible 2 min after actual sun set.

Twinkling of stars is due to atmospheric refraction.' Explain this statement with the help of a diagram and state the reason why planets do not twinkle.

How does refraction take place in the atmosphere? Why do stars twinkle but not the planets?

Assertion Sun appears red during sunrise and sunset due to the phenomenon of refraction. Reason In refraction of light frequency of light remains unchanged.

STATEMENT -1 : If reflected or refracted ray diverge from a point, the image will be virtual. and STATEMENT - 2 : After reflection or refraction the refracted or reflected rays appear to meet at a point on principle axis. They do not actually meet at a point.

When the sun is either rising or setting and appears to be just in the horizon, it is in fact below the horizon. The explanation for this seeming paradox is that light from the sun bends slightly when entering the earth's atmosphere as shown in figure. Assume that the atmosphere has uniform density and hence uniform index of refraction n and extends to a height h above the earth's surface, at which point is abruptly stop. The angle delta above the Sun's true position is given by

A narrow beam of light passes through a slab obliquely and is then received by an eye. The index of refraction of the material in the slab fluctuates slowly with time. How will it appear to the eye? The twinkling of stars has a similar explanation.