A point charge $+Q$ is placed just outside an imaginary hemispherical surface of radius R as shown in the figure. Which of the following statements is/are correct?

A) Flux passing through curved surface + Flux passing through flat surface = 0

  $$\begin{gathered} \varphi =\frac{-Q}{4\pi {\epsilon }_0}2\pi \left(1-\cos \theta \right) \\ Put \theta =45° \end{gathered}$$
 $=\frac{-Q}{2{\in }_0}\left(1-\frac{1}{\sqrt{2}}\right)$
     
 

B) at $x\&r$ is variable: E
 

$$\begin{gathered} E_{\perp }=E\sin \alpha \\ =\frac{kQ}{r^2}\frac{R}{r} \\ =\frac{KQR}{r^3} \end{gathered}$$

$E_{\perp }$ is not constant over the surface

C) Total flux through the curved and the flat surface is zero, because enclosed charge is zero.

D)  $V=\frac{kQ}{r}=\frac{kQ}{R\sqrt{2}}$ . Circumference is equidistance from charge Q. Therefore it will be equipotential surface