# Measuring thickness of tube

1. Jun 4, 2005

### Mk

I was going though one of those aquariums where you can walk through a plastic tube and can see the sea creatures up close without getting wet.

How could I find an approximate thickness of the tube just with my eye and something I can bring, like a flashlight, ruler, protractor, or whatever.

There is no given information.

2. Jun 6, 2005

### Mk

What? Not even a comment?

3. Jun 6, 2005

### brewnog

If I were you, I'd just go through the procedures the designers went through. Design the tunnel yourself, and see what value of thickness you get. Stick in a factor of safety, and there you go!

4. Jun 6, 2005

### Chi Meson

IF you knew the material the tube was made of, you could look up the index of refraction. You could assume approximately n= 1.5, but you could be much more precise if you knew which kind of plastic it was.

With a protractor, a ruler and a penlight laser, shine the laser at an angle. NOte the point on the first surface the the laser goes through (call this point 1), and record the incident angle. Note the point on the inside surface that the laser hits (call this point 2).

Draw an imaginary perpendicular line from point 2 to the first surface, call this point 3.
Measure the distance from point 3 to point 1. Use Snell's law and to find the angle of refraction. Use trigonometry to find the distance from point 2 to point 3.