Answer the following :
(a) The triple-point of water is a standard fixed point in modern thermometry. Why ? What is wrong in taking the melting point of ice and the boiling point of water as standard fixed points (as was originally done in the Celsius scale) ?
(b) There were two fixed points in the original Celsius scale as mentioned above which were assigned the number `0^(@)C" and "100^(@)C` respectively. On the absolute scale, one of the fixed points is the triple-point of water, which on the Kelvin absolute scale is assigned the number 273.16 K. What is the other fixed point on this (Kelvin) scale ?
(c ) The absolute temperature (Kelvin scale) T is related to the temperature `t_(c)` on the Celsius scale by
`t_(c)=T-273.15`
Why do we have 273.15 in this relation, and not 273.16 ?
(d) What is the temperature of the triple-point of water on an absolute scale whose unit interval size is equal to that of the Fahrenheit scale ?

Explanation

The temperature 273.16 K corresponds to the triple point of water. The Celsius scale is based on the ice point `(0^@C)` and steam point `(100^@C)` of water. The corresponding value of ice point on absolute scale is 273.15 K not 273.16 K. Therefore, `t_c = T_K - 273.15`