Why is it difficult to see through fog?

Fog consists of tiny water droplets suspended in the air near the ground [c1][c3]. Visibility is significantly reduced in fog because light rays are scattered by these droplets [c2][t3]. Specifically, when light strikes particles like water droplets or dust, it undergoes diffuse reflection and scattering, making the path of the beam visible but obscuring the objects behind the fog [c2]. This phenomenon is primarily characterized as Mie scattering, which occurs when the size of the scatterer (fog droplets are typically 10µm to 40μm) is larger than or comparable to the wavelength of light [t2][t3]. This scattering is not uniform; it involves significant forward and backward scattering, which creates a 'glare' that further reduces contrast and visual range [t3][t5]. While some absorption or reflection occurs, the primary reason for the difficulty in seeing through fog is the multidirectional scattering of light [t5][t8].

Sources

1. [1] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 10: Water in the Atmosphere > Fog and Mist > p. 87
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 10: The Human Eye and the Colourful World > 10.6.1 Tyndall Effect > p. 169
3. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 24: Hydrological Cycle (Water Cycle) > Fog > p. 332
4. [4] https://www.sciencedirect.com/topics/physics-and-astronomy/mie-scattering