how can you tell if a pair of sunglasses in polarizing?

Answer 1

If you are purchasing new sun glasses and want polarized lenses, take 2 pair and hold one with the ear pieces in the normal way they would be worn and put the others in front or behind cross ways and look through both sets of lenses.. there should be no light coming through them. You can test this by moving one set or the other to the same angle to where they match and the light will come through. (This only works with polorized lenses on BOTH pair of sun glasses).

Answer 2

Take two pair in the shop and look through both. Then turn one pair by a right angle. If the view dims you have polarising sunglasses.

Answer 3

Look through one of the lenses at a source of light reflected off a polished surface.

(Not a mirror, that doesn't work. It has to be something like a polished desk top or the surface of water, something like that)

If the lens is polarizing, the intensity of the reflection will vary as you rotate the lens.

Answer 4

if you have a cell phone (or any LCD display), while looking at the display throught the glasses rotate the phone, if glasses are polarized the display should become difficult to see.

Answer 5

look at a dim light
and at arms length turn 90 degrees