Simple mathematical problem


by Mechatron
Tags: ellen, equation, exp(), math, mathematical, simple
Mechatron
Mechatron is offline
#1
Feb5-14, 11:36 AM
P: 38
Is this equation equal to:

(e^(hf/kT)) - 1

or

e^( (hf/kT) - 1 )

http://s29.postimg.org/le6iqy3rb/exp.png
Phys.Org News Partner Mathematics news on Phys.org
Researchers help Boston Marathon organizers plan for 2014 race
'Math detective' analyzes odds for suspicious lottery wins
Pseudo-mathematics and financial charlatanism
economicsnerd
economicsnerd is offline
#2
Feb5-14, 11:46 AM
P: 206
The former.
Mark44
Mark44 is online now
#3
Feb5-14, 12:05 PM
Mentor
P: 20,971
Quote Quote by Mechatron View Post
Is this equation equal to:

(e^(hf/kT)) - 1

or

e^( (hf/kT) - 1 )

http://s29.postimg.org/le6iqy3rb/exp.png
First off, what you wrote is NOT an equation. An equation always has an = symbol in it.

The image in the link is [exp(hf/kT) - 1].

What you have written is ambiguous, as what you probably meant is this:
$$e^{\frac{hf}{kT} - 1}$$

What you actually wrote, though, is this:
$$e^{\frac{hf}{k}T - 1}$$

The brackets - [] - around the entire expression are unnecessary.

DrClaude
DrClaude is offline
#4
Feb5-14, 01:47 PM
Sci Advisor
PF Gold
DrClaude's Avatar
P: 1,111

Simple mathematical problem


Quote Quote by Mark44 View Post
First off, what you wrote is NOT an equation. An equation always has an = symbol in it.

The image in the link is [exp(hf/kT) - 1].

What you have written is ambiguous, as what you probably meant is this:
$$e^{\frac{hf}{kT} - 1}$$

What you actually wrote, though, is this:
$$e^{\frac{hf}{k}T - 1}$$

The brackets - [] - around the entire expression are unnecessary.
Why did you put the -1 in the exponential? The parenthesis limit the argument of exp to hf/kT.

My guess is that Mechatron did not write that himself, but saw it in a book. It's most probably related to the Planck distribution (blackbody radiation). As economicsnerd said, the correct reading is
$$
e^{\beta h f} - 1 \mbox{ where } \beta = \frac{1}{kT}
$$
The additional bracket [] might be there because it is part of a greater equation.
Sidney
Sidney is offline
#5
Feb15-14, 09:58 AM
P: 4
Im sorry to be off topic but I'm using a i device and i can't see (what i think to be) mathematical symbols that are in this thread... They appear as dollar signs and other randoms, i was wondering if maybe I'm short of additional download or setting adjustments. All help is highly appreciated
Mark44
Mark44 is online now
#6
Feb15-14, 11:00 AM
Mentor
P: 20,971
Quote Quote by DrClaude View Post
Why did you put the -1 in the exponential? The parenthesis limit the argument of exp to hf/kT.
The posted image, which doesn't have the -1 term, doesn't match the expressions in the first post. In the first post Mechatron asks about these expressions:
(e^(hf/kT)) - 1

and

e^( (hf/kT) - 1 )

In any case, this is moot, as Mechatron has been banned from PF.

Quote Quote by DrClaude View Post

My guess is that Mechatron did not write that himself, but saw it in a book. It's most probably related to the Planck distribution (blackbody radiation). As economicsnerd said, the correct reading is
$$
e^{\beta h f} - 1 \mbox{ where } \beta = \frac{1}{kT}
$$
The additional bracket [] might be there because it is part of a greater equation.


Register to reply

Related Discussions
Simple mathematical induction Calculus & Beyond Homework 2
How to create a simple mathematical model! General Math 14
Help with simple proof by mathematical induction Calculus & Beyond Homework 2
a mathematical model for this simple problem? Calculus & Beyond Homework 4
a simple mathematical problem Math & Science Software 3