Question

What is the angle of incidence of a ray if the reflected ray is at an angle of ${90}^o$ to the incident ray?

• A. ${30}^0$
• B. ${45}^0$
• C. ${180}^0$
• D. ${90}^0$
• E. ${60}^0$

Answer 1

Answer: (B)

${45}^0$

According to the law of reflection, the angle of incidence is equal to the angle of refraction.

That is, $\angle i=\angle r$. Let it be $x.$

In this case, the difference between the angle of incidence and angle of refraction is 90 degrees.

Given, $\angle i+\angle r$ = 90 degrees

or, $x+x={90}^0$

or, $x={45}^0$

Hence, the angle of incidence is ${45}^0$