We observe geometrical shadow of an opaque object when light is incident on it. This is due to _________.

Correct option is C

Correct Answer:C. Light travelling in a straight line

Explanation:
The formation of a geometrical shadow occurs because light travels in a straight line. When light is incident on an opaque object, the object blocks the light, and a shadow is formed behind it due to the linear propagation of light.

Key Points:

1. Rectilinear Propagation of Light: Light rays travel in straight paths, leading to well-defined shadows of objects.
2. Opaque Objects: These objects completely block the passage of light, resulting in sharp and geometrical shadows.
3. Size and Sharpness: The size and sharpness of the shadow depend on the distance between the light source, object, and screen.

Other Options Explained:

• Diffraction of Light: Diffraction refers to the bending of light around the edges of an object, which causes blurring of shadows but does not create geometrical shadows.
• Dispersion of Light: Dispersion involves the splitting of light into its constituent colors (e.g., through a prism), unrelated to shadow formation.
• Reflection of Light: Reflection occurs when light bounces off a surface, not when it forms a shadow.