Assertion: galvanometer's mirror | /r/HasProperty | fixed to moving needle
Facets:
Source sentences:
text: Helmholtz's galvanometer had a mirror fixed to the moving needle, which was used to project a beam of light onto the opposite wall, thus greatly amplifying the signal.
text: Helmholtz's galvanometer had a mirror fixed to the moving needle, which was used to project a beam of light onto the opposite wall, thus greatly amplifying the signal.