What is the angle of incidence of a ray if the reflected ray is at an

1.	What is the angle of incidence of a ray if the reflected ray is at an angle of 90° to the incident ray..?
Answer» $\textbf{ sᴏʟᴜᴛɪᴏɴ :-}$ $\implies\angle i = \angle r$ $\implies \angle i \: + \: \angle r = 90 \degree$ $\implies \angle i \: + \: \angle i = 90 \degree$ $\implies 2 \angle i = 90 \degree$ $\implies \angle i = \frac{90 \degree}{2} = 45 \degree$ $the \: angle \: of \: incidence \: is \: 45 \degree$