Units And Measurement

The refractive index is a dimensionless quantity and has no units. It is the ratio of the speed of light in a vacuum to the speed of light in a medium, and therefore, it is a pure number without any physical units

The correct option is (D): refractive index

The specific heat of the substances are as follows:
Water:
Glass:
Iron:

The correct option is (A): (a) – (ii), (b) – (iii), (c) – (i)

It is a known fact that: This is the standard conversion factor between calories and joules. Thus, the correct answer is .

The unit of electric charge is ampere-second (A·s), which is derived from the definition of current. Electric charge is the product of current and time, where: Therefore, the unit of electric charge is ampere-second (A·s). This makes option (C) the correct answer. The other options correspond to:
Electric current, which has the unit ampere (A).
Electric potential, which has the unit volt (V).
Electromotive force, which also has the unit volt (V).

The correct option is (C): electric charge

The C.G.S. unit of heat energy is the calorie.
The joule is the SI unit of energy, including heat energy.
The kelvin is the unit of temperature.
The dioptre is the unit of optical power.