  In this paper, we revisit the solar system tests of f(R) gravity. When the
Sun sits in a vacuum, the field f' is light, which leads to a metric different
from the observations. We reobtain this result in a simpler way by directly
focusing on the equations of motion for f(R) gravity in the Jordan frame. The
discrepancy between the metric in the f(R) gravity and the observations can be
alleviated by the chameleon mechanism. The implications from the chameleon
mechanism on the functional form f(R) are discussed. Considering the analogy of
the solar system tests to the false vacuum decay problem, the effective
potentials in different cases are also explored. The combination of analytic
and numerical approaches enables us to ascertain whether an f(R) model can pass
the solar system tests or not.
