Estimate the percent error in measuring a distance of about 75 cm with a metre stick

The speed of light in a material is 0.50 c. what is the critical angle of a light ray at the interface between the material and a vacuum?

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An electric current is flowing through the cord below.what will happen to this current if a magnet is brought near the cord? a. the electric current will stop flowing. b. it will exert a force on the voltage. c. the resistance of the wire will decrease. d. it will exert a force on the electric current.