Question

1. What is the shadow in physics?

2. How does it form?

3. Can shadow have a shadow?

4. Can light have a shadow ?

5. Can fire have a shadow?

6. What is shadow speed?

7. What are other properties for a shadow ?

Answer 1

We can see an object because of the light coming from the object .It might be due to

1) light produced by the object

Eg : a light bulb,sun ,stars

2) the light reflected by the object (light from some source should fall on the object for this to happen .That's why we can't see a book in a dark room)

Eg: a tree under sunlight

If theres a second object in the path of the light (which if not directly falls on the first object) .Some part of light is obstructed before reaching the first object and thus there will be a shadow (which is obviously the absence of light) of the second object on the first object .

Ps: assume wall is your first object and a person as second object.

This phenomenon can be observed because light rays can't bend( of course that is true on when obstacles are bigger than wavelength, which is generally true in real life situations)

From the above discussion it can be easily understood that a shadow can't have a shadow because it can't obstruct light .

Yes fire can have a shadow.A traditional flame can block or redirect light just fine for the simple reason that a traditional flame is more than just a pillar of light. A traditional hydrocarbon flame contains several components: hydrocarbon fuel molecules and oxygen molecules that are in the process of burning, little solid bits of half-burnt fuel and impurities (called soot or smoke), carbon dioxide and water vapor produced by the burning, light, and hot air. The light that you see in the flame is mostly created by the solid bits of airborne soot heating up so much that it glow via regular incandescence. The interface between the hot air in the flame and the colder surrounding air tends to bend light away from its forward-propagating direction. This deflection of light at the interface of different materials is called refraction. It is the same effect that enables a lens to focus light. Therefore, for the simple reason that a flame contains hot air, it is able to deflect away some of the light in a light beam and cast its own shadow. Hot air tends to rise turbulently. For this reason, shadows created by hot air tend to look like a bunch of dancing ripples. Also, the soot in a flame can absorb light and can therefore also contribute to the creation of a shadow of the flame.

The speed of shadow depends on the position of source of light if the source of light is sun at midnoon (exactly on the head) then shadow has the same speed as person in other cases it might expand ,contract.