When light is reflected by a mirror, the angle of incidence is always

When mirror reflects a ray of light, the angle of incidence is always equal to the angle of reflection ( ∠i= ∠r).

When ray of light falls on a reflecting surface, it is sent back by that surface. This is called reflection of light. The light ray falling on the surface is the incident ray whereas the ray reflected by the surface is called reflected ray.

When a line is drawn (at the point of incident ray) perpendicular to the plane of mirror, the angle formed by incident ray with the normal (perpendicular line) is called angle of incidence and the angle formed by the ray that is reflected is called angle of reflection.

As per the second law of reflection-  

Angle of incidence is always equivalent to the reflected angle.    

∠i= ∠r

so here is the information for current research:

-nrel's geothermal analysts, scientists, and engineers perform a full range of research from developing advanced methods of locating and accessing geothermal resources to exploring innovative technologies to extract and produce clean energy from the heat of the earth

and here is the information for the technology of geothermal energy:

-it's clean and sustainable

-resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma

-almost everywhere, the shallow ground or upper 10 feet of the earth's surface maintains a nearly constant temperature between 50° and 60°f (10° and 16°c)

-geothermal heat pumps can tap into this resource to heat and cool buildings

-a geothermal heat pump system consists of a heat pump, an air delivery system (ductwork), and a heat exchanger-a system of pipes buried in the shallow ground near the building

-in the winter, the heat pump removes heat from the heat exchanger and pumps it into the indoor air delivery system

-in the summer, the process is reversed, and the heat pump moves heat from the indoor air into the heat exchanger

-the heat removed from the indoor air during the summer can also be used to provide a free source of hot water