question_answer

In defining the standard of lengthy we have to specify the temperature at which the measurement should be made. Are we justified in calling length a fundamental quantity, if another physical quantity (temperature) has to be specified in choosing a standard?

Answer:

                The length of an object changes with temperature, but the unit for measuring length (i.e., metre) has now been defined in terms of wavelength of light. This is not affected by temperature. Hence, the choice of length as a fundamental unit is justified.