Radiation of Body: Is It True?

[Karan Punjabi]

Guys I have little doubt and I want you to rectify that Am I wrong or right. I think anybody at room temp or any temp emits each and every type of radiation but intensity of radiation is less for high wavelength or low wavelength waves at room temp and intensity is good enough for visible light. I am asking this on understanding of black body.

 

[benny_91]

Guys I have little doubt and I want you to rectify that Am I wrong or right. I think anybody at room temp or any temp emits each and every type of radiation but intensity of radiation is less for high wavelength or low wavelength waves at room temp and intensity is good enough for visible light. I am asking this on understanding of black body.

Intensity usually comes to picture only when the body is not diffuse. In that case body will have different intensities in different directions. I think what you are talking about is the distribution of thermal radiations over the electromagnetic spectrum when the body is at constant temperature. Let us consider a diffuse body for simplicity. A body at a certain temperature emits radiation over a wide range of wavelengths. But there will be a certain wavelength about which the energy emitted per unit area of the emitting body is maximum. Now if you increase the temperature of the body this wavelength, about which energy emission is maximum, decreases. This shift in wavelength associated with maximum energy radiation with an increase in temperature is called Wein's Displacement.

 

[Karan Punjabi]

Intensity usually comes to picture only when the body is not diffuse. In that case body will have different intensities in different directions. I think what you are talking about is the distribution of thermal radiations over the electromagnetic spectrum when the body is at constant temperature. Let us consider a diffuse body for simplicity. A body at a certain temperature emits radiation over a wide range of wavelengths. But there will be a certain wavelength about which the energy emitted per unit area of the emitting body is maximum. Now if you increase the temperature of the body this wavelength, about which energy emission is maximum, decreases. This shift in wavelength associated with maximum energy radiation with an increase in temperature is called Wein's Displacement.

Yeah i know Wein's law of displacement..but I want to ask that suppose I have a cell phone in my hand so would a normal object like cell phone would emit all types of radiations?

 

[jbriggs444]

Yeah i know Wein's law of displacement..but I want to ask that suppose I have a cell phone in my hand so would a normal object like cell phone would emit all types of radiations?

Yes. Though the rate at which hard gammas are emitted will be exceedingly low.

Google for Plank's law and the Ultraviolet Catastrophe.