The graph $AB$ shown in figure is a plot of temperature of a body in degree Celsius and degree Fahrenheit. Then

Two substances $A$ and $B$ of equal mass $m$ are heated at uniform rate of $6\,cal\,s^{-1}$ under similar conditions. A graph between temperature and time is shown in figure. Ratio of heat absorbed $H_A/H_B$ by them for complete fusion is

Explain why :

$(a)$ a body with large reflectivity is a poor emitter

$(b)$ a brass tumbler feels much colder than a wooden tray on a chilly day

$(c)$ an optical pyrometer (for measuring high temperatures) calibrated for an ideal black body radiation gives too low a value for the temperature of a red hot iron piece in the open, but gives a correct value for the temperature when the same piece is in the furnace

$(d)$ the earth without its atmosphere would be inhospitably cold

$(e)$ heating systems based on circulation of steam are more efficient in warming a building than those based on circulation of hot water

The temperature of a body on Kelvin scale is found to be $X\;K$. When it is measured by a Fahrenheit thermometer, it is found to be ${X^0}F$. Then $X$ is

Compared to a burn due to water at $100\,^oC,$ a burn due to steam at $100\,^oC$ is

Water is used to cool radiators of engines in car because