What is the angle between the horizontal surface and the incident beam, if the angle of reflection of light is 20 °?

The angle of incidence of light is equal to the angle of reflection from the surface. Moreover, the angle of incidence refers to the angle formed by a ray of light and perpendicular to the surface from which the ray is reflected. Accordingly, if the reflection angle is 20 °, then the angle between the horizontal surface and the incident beam will be equal to:
90 ° – 20 ° = 70 °

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