If a magniying glass is held under water will it magnify more, the same, or less?

Answer 1

It will magnify less. Here's why.

The index of refraction of air is 1.00
The index of refraction of water is 1.33
The index of refraction of glass is usually around 1.50

A glass lens relies on its curved shape and its higher index of refraction (compared to air) to bend light rays and thus magnify an image. The amount it is able to bend these rays increases as the ratio of the indices of refraction increases. A transition from air (i = 1.00) to a curved glass lens (i = 1.50) will yield more bending of light rays than a transition from water (i = 1.33) to the same glass lens.

You'll get no magnification at all if you submerged the lens in a liquid that had the same index of refraction as the glass!

Index of refraction is a measure of the factor by which light slows down in a medium. An index of refraction of 1 means it doesn't slow down light at all. An index of 2 means the light travels at 1/2 normal speed. An index of 1.5 means the light travels at 67% its normal speed.

Answer 2

The focal length will inc according to Snell's law.
The Magnification power is inversily proportional to the focal length
Hence the Magnification power will decrease

Answer 3

lithium dude has it right, the smaller diff in the indices of refraction between water and air will bend the rays less, causing a larger spot....less mag

Answer 4

There's a brand new invention to help you answer this; it's called an experiment. Try it; it's more fun than just thinking about it.