Question

A solid metal sphere is 15.0 cm in diameter and has surface of uniform color.When its surface is at 112°C, you measure that it radiates energy at a rate of71.3 W. What is the emissivity of the surface of this object

Answer 1

The emissivity of the surface of this object is 0.809.

Step-by-step explanation:

Given that,

Diameter = 15.0 cm

Temperature = 112°C

Power = 71.3 W

We need to calculate the area

Using formula of area

`A=4\pi r^2`

Put the value into the formula

`A=4\pi((15.0*10^(-2))^2)/(4)`

`A=0.0707\ m^2`

We need to calculate the emissivity of the surface of this object

Using formula of the emissivity

`P=\epsilon \sigma AT^4`

`\epsilon=(P)/(\sigma AT^4)`

Where, A = area

T = temperature

`\sigma` =Stefan Boltzmann constant

P = power

Put the value into the formula

`\epsilon=(71.3)/(5.670*10^(-8)*0.0707*(112+273)^4)`

`\epsilon=0.809`

Hence, The emissivity of the surface of this object is 0.809.