Gravitational frequency-shift and deflection of light by quintessence

In this paper we investigate the gravitational frequency-shift anddeflection of light in the Schwarzschild black hole space-timesurrounded by quintessence. With the analytical and numericalmethods, we find that the gravitational frequency-shift of light inthe Schwarzschild black hole space-time surrounded by thequintessence increases as the values of the normalization factor $c$increases, but the gravitational frequency-shift of light decreaseswith the quintessential state parameter $ omega_{rm q}$increasing. We also calculate the deflection of light byquintessence and find that the deflection rate decreases as thevalues of the quintessential parameters $c$ and $ omega_{rm q}$increase.