How can spectra be used to identify the presence of specific elements in a substance

What was the first instrument to ever record an earthquake?

When can a theory be modified if a new type of technology allows for new observations that raise new questions? a-immediately, while the questions about the theory are being asked b-after new hypotheses related to the theory are tested in experiments c-only after the new observations disprove all parts of the theory d-while scientists begin to think about how the theory could improve

Orque can be calculated by multiplying the force (n) applied at 90∘ to the lever arm at a distance (m) from the pivot point (point of rotation), the compound si unit for the torque is n⋅m. if the force (at 90∘ to the lever arm) applied is 15 n and it is applied at 2.0 m from the pivot point (point of rotation), what is the torque on the lever?