Question

What are luminous and Non- luminous objects?

Answer 1

Hint: Luminous intensity – The luminous intensity is represented by (\[{I_v}\]). Luminous intensity is the measure of the light-emitting ability of a light source, either generally or in a particular direction. It is measured in Candelas.

Complete answer:
Luminous objects:- The objects that can emit light energy by themselves are known as luminous objects.
Objects like the sun that give out or emit light of their own are luminous objects.
Other examples of luminous bodies are Electric bulb, torch etc.
Non-luminous objects:- the objects that can not emit light energy by themselves are known as Non- luminous objects.
Objects like the moon that do not give out or emit light of their own are Non- luminous objects.
Moon is an example of a non-luminous object as we can see the moon because it reflects light from the sun.
Other examples of Non luminous bodies are pen, pencil, chair, wood etc.
Luminosity – It is defined as the luminous intensity in a particular direction; or we can say it is the apparent brightness of an image.
The brightness of a star is defined as the total energy radiated in unit time. It is related to the surface area (A) and the effective temperature ($T$) ( the temperature of a black body having the same radius as the star and radiating the same amount of energy per unit area in one second ) by a form of Stefan’s law, here is given by
\[ \Rightarrow L = A\sigma {T^4}\]
where \[\sigma \] is the Stefan’s constant and $L$ is the luminosity.

Note:
The laptop screen, mobile screen you are looking at right now is luminous but the page of your book is a non-luminous object, which is why you need a light on to read it.