What angle does a normal make with the opaque surface?

Options

A. `45^@`
B. `90^@`
C. `60^@`
D. `100^@`

Answer

To determine the angle that a normal makes with an opaque surface, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Normal Line**: The normal line is defined as the line that is perpendicular to the surface at the point of incidence where light strikes the surface.

2. **Identifying the Surface**: In this case, we are dealing with an opaque surface. An opaque surface is one that does not allow light to pass through it, meaning that light will either be reflected or absorbed.

3. **Reflection vs. Refraction**: Since the surface is opaque, we will consider the phenomenon of reflection rather than refraction. Refraction occurs when light passes from one medium to another, which is not applicable here.

4. **Defining the Angle**: The angle that the normal makes with the surface is always 90 degrees. This is because the normal is defined as being perpendicular to the surface.

5. **Conclusion**: Therefore, the angle that the normal makes with the opaque surface is 90 degrees.

### Final Answer:
The angle that a normal makes with the opaque surface is **90 degrees**.

---