Chemical Engineering - Heat Transfer - Discussion

4. 

Which of the following is generally considered as opaque surface towards radiations?

[A]. Gases
[B]. Solids
[C]. Liquids
[D]. Both (b) and (c)

Answer: Option D

Explanation:

No answer description available for this question.

Neha said: (Jul 2, 2012)  
Then how does the sunlight reach to the aquatic plants.

Troy said: (Aug 25, 2013)  
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.

Gaurav said: (Dec 19, 2013)  
Most solids are opaque to thermal radiation except glass, rock salt etc.

Many liquids and gases are transparent to thermal radiation.

Dumbi said: (May 20, 2014)  
Gases also absorbed heat. Should they not be considered opaque?

Shankar said: (Nov 30, 2014)  
Then why liquid is opaque?

Dinesh said: (Mar 6, 2016)  
Yes. Liquids are transparent to radiation. But it is an engineering consideration that they are opaque.

Refer introduction to heat transfer by incropera.

Ananth C said: (Dec 24, 2016)  
Well, Visible light is also an electromagnetic wave which can propagate through liquids. Then why liquid considered as opaque?

Saa said: (Oct 31, 2018)  
Opaque (means) : not able to be seen through; not transparent.

Uday said: (Dec 18, 2018)  
Why Liquid is not transparent?

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