project to find the factors affecting focal length when liquids acts as lenses?

Answer 1

Just as with any other kind of lens, the shape of the lens will be one of the parameters that affects the focal length, but I’ll assume you will use the same-shaped container to look at the differences between different liquids. (The material that the container is made of will also affect the focal length, but I’ll also assume that’s constant, too.)

In this case, there are really only three things that matter, and if you use a single color light source (e.g., a red laser pointer), only the first matters. Even if you don’t, the second parameters listed below are normally of much less importance than the first.

1.The refractive index of the liquid
2.The chromatic dispersion of the liquid
3.The wavelength (color) of the light being sent through the lens.

The primary parameter is the refractive index; which quantifies the extent to which a light ray is refracted (“bent”) as it crosses the interface with the liquid and whatever is on the other side of the liquid (i.e. the container material). For a given shaped lens, a higher refractive index liquid will cause more refraction, and hence result in a “stronger” lens.

The chromatic dispersion tells you how much the refractive index varies as a function of the wavelength of the light. All real materials have some dispersion, and because the refractive index for different colors of light are slightly different, the focal length and focal point of any real lens is slightly different for different colors. (Manufacturers of things like high-quality camera lenses take great pains to minimize the dispersion of their lenses by using multiple optical elements (individual lenses) made of different materials.)

Finally, because the index of refraction varies as a function of wavelength, the focal length will also depend on the wavelength of the light you use.

If we ignore the last two effects (e.g., let’s say you use a laser pointer as the light source, we can concentrate on how you might vary the refractive index of liquid you use. First, different liquids have different refractive indices because they have different chemical compositions and molecular makeups. Materials have characteristic refractive indices because of the way light interacts with the atoms and molecules making up the liquids. Different molecules interact with light in different ways, giving rise to differences in refractive index.

Your first experiment might then look at different composition liquids (oil, water, alcohol, water containing the same concentration of different dissolved substances, water containing different concentrations of the same substance, etc.).

Second, to a much lesser extent, the refractive index of a material depends on temperature (mostly because the density of materials depends on temperature). You could try looking at the effect of heating the same fluid to different temperatures and seeing if that makes a measurable difference in the focal length. Different fluids will have different temperature dependences.

Answer 2

Index of refraction of the liquid

Answer 3

Viscosity, purity, temperature, angle of contact.

There are a lot of factors to be considered.