which of the following best defines insulator?

What produces light and all other electromagnetic waves? a) the photoelectric phenomena b) heated metals c) charged particles d) radioactive samples (pls explain if you can : )

Aforce of 34n stretches a very light ideal spring 0.73 m from equilibrium, what is the force constant (spring constant) of the spring? (a) 47n/m (b) 38n/m (c) 53n/m (d) 25n/m

In a vernier instrument the main scale is in 1/2 mm divisions .vernier is made by redividing 19 such divisions into 20 equal parts. calculate the least count of the instrument.