The Maths and Science Thread - Collection of Problems and Facts

[ste_mc_efc]

i'm debating not doing my quantum mechanics uni work and claiming that the worksheet is an eigenvalue!

 

[Varun]

what is an eigenvalue?

 

[ste_mc_efc]

what is an eigenvalue?

actually meant to type eigenfunction.

It is something in quantum mechanics that remains unchanged when operated on by a certain operator.

Like if the operator is to differentiate twice for sin kx or something.

 

[Chewie]

I did eigenvalues in maths last year but I can't quite remember what they're about... matrices?

 

[ste_mc_efc]

I did eigenvalues in maths last year but I can't quite remember what they're about... matrices?

not sure about that, we basically only learn them in relation to their use in chemistry, so not an expert.

 

[Varun]

Anyone doing stats or higher maths in uni could tell me the derivation for the formulae of mode and median respectively?

 

[King Cricket]

How do you draw the circuit diagrams of NAND and NOR gates? I'm completely at a loss here. Our teacher didn't explain these to us or anything, yet one day before the exams, I get to know that the whole thing is included. I've tried googling the terms, but the results are far too complicated for me to make any head and tail of it.

 

[King Cricket]

The diagrams didn't come in the exams. Nonetheless, I'm pretty intrigued about circuit diagrams as well as logic diagrams of AND, OR, NOT, NAND, and NOR gates. I can vaguely understand the concept, but a clear explanation will be appreciated.

 

[AbhishekS]

NOR means Negative/Not OR

and

NAND means Negative/Not AND.

They are represented just by adding a small circle ahead of the symbol of OR and AND gates respectively.

The term "Negative (N)" says it all that they just negate the result.


For example:

AND gate
Input 1 - Input 2 - Output
0 - 0 - 0
0 - 1 - 0
1 - 0 - 0
1 - 1 - 1

NAND gate
Input 1 - Input 2 - Output
0 - 0 - 1
0 - 1 - 1
1 - 0 - 1
1 - 1 - 0

---

OR gate
Input 1 - Input 2 - Output
0 - 0 - 0
0 - 1 - 1
1 - 0 - 1
1 - 1 - 1

NOR gate
0 - 0 - 1
0 - 1 - 0
1 - 0 - 0
1 - 1 - 0

 

[King Cricket]

Well, what is the precise function of these logic gates in computer science? I mean how exactly do they help in data transmission?

And how do you draw the circuit diagrams of NAND and NOR?

 

[AngryPixel]

They are used in flip flops and memory cells. You can get a better explanation in a Digital Electronics book. You can easily find one in your uni's library. Another use of these gates is in PLC(programmable logical controller).

AngryPixel added 1 Minutes and 55 Seconds later...

They are used in flip flops and memory cells. You can get a better explanation in a Digital Electronics book. You can easily find one in your uni's library. Another use of these gates is in PLC(programmable logical controller).

multiplexers,demultilexers, interfacing between microprocessors etc

 

[AbhishekS]

Are photons mass-less?

 

[AngryPixel]

What does GJ/te unit means? there is a table in my book which shows the heat content of gases in this unit

 

[Varun]

Are photons mass-less?

They are packets of light. And light has dual nature i.e. both of matter and waves, so they must have a mass..?

 

[AbhishekS]

They are packets of light. And light has dual nature i.e. both of matter and waves, so they must have a mass..?

If the have any mass, then the light coming out from tube-lights and bulbs should get over as time progresses. So, this gives a strong feeling that they must be mass-less.

Secondly, light cannot come out from a blackhole as the escape velocity of a blackhole is much higher than the velocity of light. Also, gravity acts on light waves. These two reasons give an impressions that the photos must have some mass.

Pretty confused about it. This topic isn't giving me any sleep for the past two days now.