Q. The tail of a comet is directed away from the sun because?
Answer: the radiation emitted by the sun exerts a radial pressure on the comet throwing its tail away from the sun
Notes: The streams of dust and gas thus released from a huge, extremely tenuous atmosphere around the comet called the coma, and the force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun.