Q. When the emissivity of non-black surface is constant at all temperatures and throughout the entire range of wavelength, the surface is called

View solution

Q. The emissivity of the gray surface may be expressed as

View solution

Q. If a black body at 1000 K and a gray body at 1250 K emit the same amount of radiation, what should be the emissivity of the gray body?

View solution

Q. The radiant heat transfer from a plate of 2.5 cm² area at 1250 K to a very cold enclosure is 5.0 W. Determine the emissivity of the plate at this temperature

View solution

Q. A 100 W light bulb has a tungsten filament (emissivity = 0.30) which is required to operate at 2780 K. If the bulb is completely evacuated, calculate the minimum surface area of the tungsten filament

View solution

Q. For a hemisphere solid angle is measured as

View solution

Q. A gray body (E = 0.8) emits the same amount of heat as a black body at 1075 K. Find out the required temperature of the gray body

View solution

Q. The heat energy absorbed by a known area in a fixed time is determined with the help of an instrument called

View solution

Q. The value of solar constant varies between

View solution

Q. The total amount of heat energy received by the sphere of radius r is

View solution

Q. Amount of heat energy radiated by unit surface of the sun in the same time workout as
Take, R = mean distance of earth from the sun and r = radius of sun

View solution

Q. Temperature of sun can be workout from

View solution

Q. The temperature of the photosphere, referred to as the effective temperature of the sun, is usually taken as

View solution

Q. The approximate distribution of the flow of sun’s energy to the earth’s surface is

View solution

Q. The solar radiation that is felt at the earth’s surface includes

(i) Direct radiation that has passed through the atmosphere

(ii) Diffuse radiation from the sky

(iii) Absorbed radiation from the water

Identify the correct statement

View solution

Q. When the sun lies at a mean distance from the earth, the heat flux from the sun to the outer edge of the atmosphere has been found to be

View solution

Q. Which one is having highest value of solar absorptivity?

View solution

Q. What is the value of solar absorptivity for aluminum foil?

View solution

Q. What is the value of solar absorptivity for polished copper?

View solution

Q. Which one is having lowest value of solar absorptivity?

View solution