Weak Deflection Angle, Hawking Radiation, Greybody Bound and Shadow Cast for Static Black Hole in the Framework of $f(R)$ Gravity

Abstract: In this work, we probe the weak gravitational lensing by a static spherically symmetric black hole in view of $f(R)$ gravity in the background of the non-plasma medium (vacuum). We provide a discussion on a light ray in a static black hole solution in $f(R)$ gravity. To adore this purpose, we find the Gaussian optical curvature in weak gravitational lensing by utilizing the optical geometry of this black hole solution. Furthermore, we find the deflection angle up to the leading order by employing the Gauss-Bonnet theorem. We present the graphical analysis of the deflection angle with respect to the various parameters that govern the black hole. Further, we calculate the Hawking temperature for this black hole via a topological method and compare it with a standard method of deriving the Hawking temperature. We also analyze the Schr\"odinger-like Regge-Wheeler equation and derive a bound on the greybody factor for a static black hole in the framework of $f(R)$ gravity and graphically inquire that bound converges to 1. We also investigate the silhouette or shadow generated by this static $f(R)$ black hole. Moreover, we constrain the non-negative real constant and cosmological constant from the observed angular diameters of M87* and Sgr A* released by the EHT. We then probe how cosmological constant, non-negative real constant and mass affected the radius of shadow. Finally, we demonstrate that, in the eikonal limit, the real part of scalar field quasinormal mode frequency can be determined from the shadow radius.