Understanding the Angle of Reflection When Light Strikes a Plane Mirror Perpendicularly

The behavior of light when it strikes a plane mirror is governed by the law of reflection. This law stipulates that the angle of incidence is equal to the angle of reflection, both measured with respect to the normal. In this article, we will explore what happens when light strikes a plane mirror at an angle of 90 degrees.

Law of Reflection

The law of reflection states that the angle of incidence is equal to the angle of reflection, where both angles are measured with respect to the normal. The normal is an imaginary line drawn perpendicularly to the surface of the mirror at the point of incidence.

Incidence at 90 Degrees

When a ray of light strikes a plane mirror at an angle of 90 degrees with respect to the normal, the angle of incidence is 90 degrees. According to the law of reflection, the angle of reflection will also be 90 degrees. This means that the reflected ray will travel back along the same path as the incident ray but in the opposite direction.

The relationship can be described as follows:

Angle of incidence Angle of reflection 90 degrees

Visual Explanation

Imagine a light ray striking a plane mirror at an angle of 90 degrees from the normal. The incident ray and the reflected ray are both perpendicular to the surface of the mirror, and they lie on the same line but in opposite directions. Therefore, the angle between the incident ray and the reflected ray is 0 degrees. This is illustrated in the diagram (not shown here) where both rays are shown as lying along the normal.

Practical Implication

In a practical scenario, if a light ray strikes a plane mirror perpendicularly, the light bounces back in the same direction. This principle has numerous applications in everyday life, such as in mirrors on walls, car rearview mirrors, and optical devices.

Conclusion

Understanding the angle of reflection when light strikes a plane mirror at an angle of 90 degrees is crucial in optics and can be applied in various scientific and practical contexts. The consistency of the law of reflection ensures that light behaves predictably and consistently, allowing us to design and use optical devices effectively.