# Thin Lenses

lha08

## Homework Statement

When 2 glass plates form an air wedge with a fine wire at one end, why don't we convert the given wavelength in air of light into the wavelength in glass since we have to convert it when it is entering in water??
Thanks

## The Attempt at a Solution

Homework Helper
Because the fringes are formed in the air gap - the experiment works just as well with two metal mirrors.

lha08
Because the fringes are formed in the air gap - the experiment works just as well with two metal mirrors.

so there are gaps in the glass that light passes through so we don't need to convert it?

Homework Helper
The experiment is to measure fringes formed in the air between the two slides.
The only reason you use glass slides is to be able to see what's happening - all the interference takes place in the air (the wedge gap) between them.

lha08
The experiment is to measure fringes formed in the air between the two slides.
The only reason you use glass slides is to be able to see what's happening - all the interference takes place in the air (the wedge gap) between them.

If water was surrounding the wedge, would we still keep using the wavelength in air for a problem like that?