Emissive power of an ideal black body at $127°\mathrm{C}$ is $E$. The temperature at which it increases to $102\%$ is

The plots of intensity versus wavelength for three black bodies at temperatures $T_1,T_2$ and $T_3$ respectively are as shown. Their temperature is such that

Three rods $AB, BC, CA$ are joined to form a triangle $ABC$. Length of the rods $AB$ and $AC$ each are equal to $b$ and their coefficient of linear expansion is ${\alpha }_1$ whereas length of $\text{rod} BC$ is $a$ and its coefficient of linear expansion is ${\alpha }_2.$ Ratio $\frac{b}{a}$, such that the height $h$ does not change upon heating the rods by same temperature, is $\frac{1}{n}\sqrt{\frac{{\alpha }_2}{{\alpha }_1}}$. Value of $n$, is