A hot isothermal metal substrate at 300°C is coated with a 5 mm acrylic (density 1990 kg/m^3 , specific heat 1470 J/kg*K, and conductivity 0.21 W/m*K) sheet, initially at 20°C. As the sheet is getting heated by contact with the metal substrate determine how long will it take for the insulated back side of the sheet to reach its softening 90°C.

Consider a large isothermal enclosure that is maintained at a uniform temperature of 2000 k. calculate the emissive power of the radiation that emerges from a small aperture on the enclosure surface. what is the wavelength ? , below which 10% of the emission is concentrated? what is the wavelength ? 2 above which 10% of the emission is concentrated? determine the wavelength at which maximum spectral emissive power occurs. what is the irradiation incident on a small object placed inside the enclosure?