The blackboard seems black because it

An object's color is determined by the wavelengths of light it reflects or absorbs. According to the principles of optics, we see objects because they reflect light into our eyes. A surface appears white when it reflects all wavelengths of the visible spectrum, whereas it appears black when it absorbs all wavelengths and reflects virtually no light. A blackboard appears black because its surface is designed to absorb almost all incident visible light rather than reflecting specific colors. Since black is essentially the absence of reflected visible light, the lack of reflection from the board's surface results in the perception of the color black. Therefore, the blackboard seems black because it does not reflect any color back to the observer's eyes.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > p. 134