Question

I am to fill in the blanks without a word bank, my answers are in brackets.

1. When light waves reflect from media in which the speed of light is slower, their phase (crest or trough) is ____

2. The trick to being able to observe interference patterns for light waves in to shine one light source through ____

Answer 1

I don't see any brackets but I see parentheses.
I don't see any answers.
I would answer the first one with "shifts".
I would answer the second one with "slits".
For #2 it's much much easier to observe interference from light waves by looking at a thin layer of oil on water.

Answer 2

When a wave travels from fast to slow medium:
Reflected wave is inverted. (crest -reflected as trough is 180 deg phase shift)