Apparent and Real Depth

Apparent and Real Depth are the depths of any object when submerged under any different medium. The actual depth of a submerged object is called real depth, and the perceived depth of any object is due to the change of medium, which is called Apparent Depth. In addition to this, there are some more key differences between Apparent and real depth. These differences are listed in the following table:

Aspect	Real Depth	Apparent Depth
Definition	The actual physical distance from an observer to an object submerged in a transparent medium.	The perceived distance from an observer to an object submerged in a transparent medium, as it appears to the observer.
Calculation	Determined based on the actual physical dimensions of the object and its position in the medium.	Influenced by the refraction of light as it passes through the boundary between two media with different optical densities.
Value	Constant and does not change with observation or medium.	Variable and can change depending on the angle of observation, the refractive index of the medium, and the position of the object.
Examples	If an object is 10 cm below the water’s surface, its real depth is 10 cm.	If an object is 10 cm below the water’s surface, its apparent depth may be less than 10 cm when viewed from above due to refraction.
Use in Optics	Used in calculations involving Snell’s law, lens equations, and other optical phenomena.	Used to explain optical illusions like the bending of a straw in a glass of water or the appearance of objects “closer” in water.
Units	Measured in meters (m), centimetres (cm), or any appropriate length unit.	Measured in the same units as real depth (m, cm), but may appear different due to optical effects.

Apparent Depth

Apparent Depth is an example of reflection of light from different mediums and can be observed in many areas. Such as when we drink water from a bottle or any vessel we have an illusion that the bottle’s base is very near to us, but after it gets empty we realize its actual depth. This illusion is a result of the phenomenon known as Apparent Depth. Apparent Depth plays a crucial role in our perception of objects submerged in liquids as there are many such examples like a fish in a pond appearing near to the surface, the bottom of the Swimming Pool appearing near to the surface, and many more.

In this article, we will dive deep into the phenomenon of apparent depth, exploring its definition, the laws of refraction governing it, its mathematical formulation, the factors affecting it, and solving a problem to solidify our understanding.

Table of Content