Why is the following situation impossible? While at the...

Key Concepts

Critical Angle and Total Internal Reflection

When light attempts to pass from a medium with a higher refractive index to one with a lower refractive index, there is a maximum incident angle—the critical angle—beyond which light cannot exit the denser medium and is instead completely reflected back. For water to air, this critical angle defines the boundary of a phenomenon known as 'Snell's window', beyond which no light from an external source can refract into the water.

Snell's Law

This fundamental law in optics relates the angles of incidence and refraction at an interface between two media with different refractive indices through the formula n? sin(??) = n? sin(??). In the context of light entering water from air (or vice versa), it governs how the apparent direction of an object (like the Sun) is altered owing to the change in speed of light as it passes from one medium to another.

Apparent Shift Due to Refraction

Because of the bending of light at the interface, objects viewed from underwater appear in positions different from their actual locations. The upward shift in the apparent position of the Sun is determined by the refraction at the water's surface, and if the measured apparent angle requires a ray from the Sun to have originated at an impossible incidence (i.e. exceeding what is allowed by the critical angle), the situation violates physical laws.

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