Understanding the Speed of Light and Magnification with a Magnifying Glass
Is the speed of light and the magnification of a magnifying glass affected by the medium it passes through?
Answer: no, the magnifying glass has nothing to do with the speed of light.
Explanation:
When light moves between 2 media (refraction), part of its properties that changes during this process is its speed. The change in speed is dependent on the refractive index of the 2 media and as given by Snell's Law, the refractive index is inversely proportional to wave speed.
This implies that moving from a dense medium to a less dense medium reduces wave speed and moving from a dense medium to a less dense medium increases wave speed. For the first statement, light moved from glass to water, implying that it moves from a dense to a less dense medium, increasing its wave speed in water.
For the second statement, light moved from glass to air, also moving from a dense to a less dense medium, increasing its wave speed in air. Given that air is less dense than water, light travels faster in air than in water. Thus, the magnification property of a glass has nothing to do with the wave speed, only the refractive indices of the media.
Understanding Refraction and Magnification:
When light travels from one medium to another, it gets refracted because the speed of light is different for different mediums. The change in speed is dependent on the refractive index of the media, and as given by Snell's Law, the refractive index is inversely proportional to the speed of light.
Air is less dense than water, leading to light traveling faster in air than in water. The same goes for glass. However, the refractive index of glass relative to water is less different, meaning the speed of light in glass relative to that in water differs lesser than with air. This does not change the refractive index of glass with respect to air.
Therefore, there will be no change in the magnifying power of the glass when used underwater.