Ask What Is on the Far Side

You'll learnwhat decides whether a reflected pulse comes back upside down, why sound cannot be polarized, and why the first filter in a polarizer stack obeys a different rule from every filter after it.

A pulse hits the join between two strings and part of it comes back upside down — but turn the trip around and the echo comes back upright. Then three polarizing filters pass more light than two. Twelve short steps; press Next for each one.

12 STEPS · 6 QUICK CHECKS · ASK THE FAR SIDE · THE FIRST FILTER DIFFERS · v2

the far side decides the flip · only transverse waves polarize

Before you start

What you're looking at

A pulse meeting the join between a light string and a heavy one, with both the reflected and the transmitted part drawn. Later, a stack of polarizing filters.

The question

What decides whether an echo comes back upside down — and why can three filters pass more light than two?

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