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# Tag Archives: definition

## What is induction and deduction?

What is induction and deduction? (Asked Anamika Singh)

Answer:

Induction and deduction are the two ways of arriving at conclusions in Philosophy.

In **induction**, you start with a limited number of observations and *increase *that number by generalizing.

in **deduction**, you start with a set of possibilities and reduce it until a smaller subset remains.

Read more at : –

- http://www.dummies.com/how-to/content/thinking-logically-deduction-and-induction.html

- http://en.wikipedia.org/wiki/Deduction_and_induction
- https://school.carm.org/amember/files/demo3/2_logic/deduction_induction.htm
- http://www.butte.edu/~wmwu/iLogic/1.3/iLogic_1_3.html

## Confusion with the definition of unit of time and distance.

Ram Kishore Bajpai asked: (The question is posted as such without rectifying errors.)

“Why is the time defined by distance traveled by light in vacuum 1/299,452,758?

Why does the people use a easier number such as 1/300,000,000? Why didn’t 1 second?”

Answer:

It seems that you are confused a little.

The distance traveled by light in vacuum in 1/299,452,758 of a second is defined as one **metre**. This is because light travels 299,452,758 m in one second in vacuum.

The value 299,452,758 m/s is the speed of light calculated by various experiments and universally accepted standard.

But ordinary situations do not demand this much level of accuracy. If you correct the value 299,452,758 m/s to 1 decimal accuracy, you will get 3.0 x 10^{8} m/s (3,00,000 m/s) and is used in ordinary calculations requiring one or two decimal places accuracy.

## Free electrons in Materials and shock?!

Sachin asks: “Sir I am not able to understand that conductors n insulators have free electron n moving randomly in direction but the definition says that FLOW OF CHARGE PER UNIT TIME IS CALLED CURRENT. SO my question is electrons are moving in both conductors or insulators but when touch them they don’t produce electric current why ???”

## Black Holes and Thermal Radiation

**Varun G asked**

“Do black holes produce thermal radiation, as expected on theoretical grounds and do they absorb light?”

**Ans**: Hope you are talking about the **Hawking radiation**.

Any body at a temperature above absolute zero emits radiations. If the temperature of black body is not absolute zero (It was Stephen Hawking who predicted that black holes should have a finite, non-zero temperature, and hence the name “Hawking Radiation”) it will emit radiation.

In a black hole emitting radiation, there is a loss of mass. If the mass decreased due to Hawking Radiation is more than the mass gained by the black holes via alternate means, the net mass of the black holes will go on decreasing. (This is called “**black hole evaporation**” Further, it has been noted that the black holes with lower mass emit more radiations than the heavier ones.

This answer may seem contradicting the definition of black hole itself.

“A black hole is a body whose gravitational force of attraction is so huge that even electromagnetic radiation cannot escape from it” as the definition goes.

But the Hawking Radiation is caused by Quantum effects. The processes behind the “escape” of radiation from a black hole is thought to be

- Vacuum Fluctuations and
- Quantum tunneling

The above terms and concept will be too high to be discussed at school level. However for the curious ones, I am giving some links to explore.

- http://www.chm.bris.ac.uk/webprojects2000/plewis/Main.html
- http://en.wikipedia.org/wiki/Black_body
- http://en.wikipedia.org/wiki/Black_hole_thermodynamics
- http://www.braungardt.com/Physics/Vacuum%20Fluctuation.htm
- http://www.newscientist.com/article/dn16095-its-confirmed-matter-is-merely-vacuum-fluctuations.html?full=true&print=true
- http://phys.educ.ksu.edu/vqm/html/qtunneling.html