The absorptivity, The transmissivity and reflectivity are given by: If the amounts of radiation energy absorbed, reflected, and transmitted when radiation strikes a surface are measured in percentage of the total energy in the incident electromagnetic waves. The total energy would be divided into three groups, they are called absorptivity (), reflectivity () and transmissivity (t). + + t = 1 (1) A body is considered transparent if it can transmit some of the radiation waves falling on its surface. If electromagnetic waves are not transmitted through the substance it is therefore called opaque. When radiation waves hit the surface of an opaque body, some of the waves are reflected back while the other waves are absorbed by a thin layer of the material close to the surface. For engineering purposes all materials are thick enough that they can be considered opaque reducing equation 1 to: + = 1 (2) Reflectivity deviates from the other properties in that it is bidirectional in nature. In other words, this property depends on the direction of the incident of radiation as well as the direction of the reflection. Therefore, the reflected rays of a radiation spectrum incident on a real surface in a specified direction forms an irregular shape that is not easily predictable. In practice, surfaces are assumed to reflect in a perfectly specular or diffuse manner. In a specular reflection, the angles of reflection and incidence are equal. In diffuse reflection, radiation is reflected equally in all directions. Reflection from smooth and polished surfaces can be assumed to be specular reflection, whereas reflection from rough surfaces approximates diffuse reflection. Considering this given object as an opaque substance, The value of transmissivity is zero So, the Absorptivity + Reflectivity = 1---(3) Assuming 100% emmitance of the absorbed body We get the value of Absorptivity = value of Emmisivity = 0.7 So, from equation (3) Reflectivity = 1 - Absorptivity Reflectivity = 1 - 0.7 = 0.3 Heat Rate Reflected per unit area is given by: Gref = G * Reflectivity = 1000 *0.3 = 300 W/m2 So, The Rate Reflected per unit area is Gref 300 W/m2 Solution The absorptivity, The transmissivity and reflectivity are given by: If the amounts of radiation energy absorbed, reflected, and transmitted when radiation strikes a surface are measured in percentage of the total energy in the incident electromagnetic waves. The total energy would be divided into three groups, they are called absorptivity (), reflectivity () and transmissivity (t). + + t = 1 (1) A body is considered transparent if it can transmit some of the radiation waves falling on its surface. If electromagnetic waves are not transmitted through the substance it is therefore called opaque. When radiation waves hit the surface of an opaque body, some of the waves are reflected back while the other waves are absorbed by a thin layer of the material close to the surface. For engineering purposes all materials are thick .

1. The absorptivity, The transmissivity and reflectivity are given by:
If the amounts of radiation energy absorbed, reflected, and transmitted when radiation strikes a
surface are measured in percentage of the total energy in the incident electromagnetic waves.
The total energy would be divided into three groups, they are called absorptivity (), reflectivity ()
and transmissivity (t).
+ + t = 1 (1)
A body is considered transparent if it can transmit some of the radiation waves falling on its
surface. If electromagnetic waves are not transmitted through the substance it is therefore called
opaque. When radiation waves hit the surface of an opaque body, some of the waves are
reflected back while the other waves are absorbed by a thin layer of the material close to the
surface. For engineering purposes all materials are thick enough that they can be considered
opaque reducing equation 1 to:
+ = 1 (2)
Reflectivity deviates from the other properties in that it is bidirectional in nature. In other words,
this property depends on the direction of the incident of radiation as well as the direction of the
reflection. Therefore, the reflected rays of a radiation spectrum incident on a real surface in a
specified direction forms an irregular shape that is not easily predictable. In practice, surfaces are
assumed to reflect in a perfectly specular or diffuse manner. In a specular reflection, the angles
of reflection and incidence are equal. In diffuse reflection, radiation is reflected equally in all
directions. Reflection from smooth and polished surfaces can be assumed to be specular
reflection, whereas reflection from rough surfaces approximates diffuse reflection.
Considering this given object as an opaque substance, The value of transmissivity is zero
So, the Absorptivity + Reflectivity = 1---(3)
Assuming 100% emmitance of the absorbed body
We get the value of Absorptivity = value of Emmisivity = 0.7
So, from equation (3)
Reflectivity = 1 - Absorptivity
Reflectivity = 1 - 0.7 = 0.3
Heat Rate Reflected per unit area is given by:
Gref = G * Reflectivity = 1000 *0.3 = 300 W/m2
So, The Rate Reflected per unit area is Gref 300 W/m2
Solution

2. The absorptivity, The transmissivity and reflectivity are given by:
If the amounts of radiation energy absorbed, reflected, and transmitted when radiation strikes a
surface are measured in percentage of the total energy in the incident electromagnetic waves.
The total energy would be divided into three groups, they are called absorptivity (), reflectivity ()
and transmissivity (t).
+ + t = 1 (1)
A body is considered transparent if it can transmit some of the radiation waves falling on its
surface. If electromagnetic waves are not transmitted through the substance it is therefore called
opaque. When radiation waves hit the surface of an opaque body, some of the waves are
reflected back while the other waves are absorbed by a thin layer of the material close to the
surface. For engineering purposes all materials are thick enough that they can be considered
opaque reducing equation 1 to:
+ = 1 (2)
Reflectivity deviates from the other properties in that it is bidirectional in nature. In other words,
this property depends on the direction of the incident of radiation as well as the direction of the
reflection. Therefore, the reflected rays of a radiation spectrum incident on a real surface in a
specified direction forms an irregular shape that is not easily predictable. In practice, surfaces are
assumed to reflect in a perfectly specular or diffuse manner. In a specular reflection, the angles
of reflection and incidence are equal. In diffuse reflection, radiation is reflected equally in all
directions. Reflection from smooth and polished surfaces can be assumed to be specular
reflection, whereas reflection from rough surfaces approximates diffuse reflection.
Considering this given object as an opaque substance, The value of transmissivity is zero
So, the Absorptivity + Reflectivity = 1---(3)
Assuming 100% emmitance of the absorbed body
We get the value of Absorptivity = value of Emmisivity = 0.7
So, from equation (3)
Reflectivity = 1 - Absorptivity
Reflectivity = 1 - 0.7 = 0.3
Heat Rate Reflected per unit area is given by:
Gref = G * Reflectivity = 1000 *0.3 = 300 W/m2
So, The Rate Reflected per unit area is Gref 300 W/m2