This question already has an answer here:
Let’s suppose a spellcaster casts Blink on himself. He then uses ready action to move freely around the ethereal plane while not on his turn. After this, when his turn starts again, he will be teleported again to the material plane, within 10ft of the original place he blinked from.
The question is, can the caster move through walls that are on the material plane while he is on the ethereal plane?
Since the blink spell sends the caster to the ethereal plane, and grants him sight into the material plane this would allow the caster to actually see what is behind those walls safely. Is this possible?