Answer:

Given:
Radius of curvature (R) of a spherical mirror = 20
To Find:
Focal length (f)
Explanation:
Formula:

Substituting value of R in the equation:



Answer
Magma is less dense compared to the surrounding rock.
the overlying rock creates pressure which forces the magma to be directed upward.
Explanation:
at high temperatures the magma is liquid form with the high energy which causes the formation of bonds and the pressure build up creates the increase channeling of the liquid.as the temperature decreases the magma moves into the surface