Question

A diode laser emits at wavelength of 744nm.
All of its output energy is absorbed in a detector that measures a total energy of .63J over a period of 47s. How many photons per second are being emitted by the laser.
I got 5.0*10^16 photons/second. Back of the book says 5.0*10^13photons/second.

Answer 1

alright one sec.

Answer 2

E=hv... h being planck's constant. v being frequency.

Answer 3

\[\lambda v = c\]

Answer 4

so \[v=c/\lambda \]

Answer 5

\[E=h(c/\lambda )\]

Answer 6

\[E=6.626^{-34}Js*3*10^{8}m/s*\frac{ 1 }{ 744*10^{-9}m }\]

Answer 7

\[2.67*10^{-19}\]

Answer 8

thats what tha equals.

Answer 9

and that's in J/photon

Answer 10

\[\frac{ .63J }{ 47s}*\frac{ photon }{ 2.67*10^{-19} J}\]

Answer 11

\[=5.0*10^{16}\]

Answer 12

photons/second

Answer 13

@Rushwr that's how I went about it i'm assuming that's the process not sure if i plugged in to the calculator properly.

Answer 14

@IrishBoy123 you good with chemistry?

Answer 15

@freckles you good with chem?

Answer 16

no but I can try to look at your problem

Answer 17

try and just plug in the numbers into a calculator and see if you get the correct answer

Answer 18

I have done that and it doesn't calculate to the back of the book
\[E=6.626^{-34}Js*3*10^{8}m/s*\frac{ 1 }{ 744*10^{-9}m }\]
where does the 6.626^(-34) come from
and the 3*10^8 come from ?

Answer 19

6.636*10^-34 is planck's constant.

Answer 20

which is denoted using h.

Answer 21

oh times 10^(-34)

Answer 22

and c is the speed of light.

Answer 23

which is the 3*10^8m/s

Answer 24

I do have one complaint

Answer 25

when you get that first part the units are in joules/photon and then you continue using dimensional analysis to get photon/second

Answer 26

what is it?

Answer 27

\[7.44 \times 10^{-7} m =744 nm\]
right?

Answer 28

yes

Answer 29

you have -9

Answer 30

not -7

Answer 31

i account for it by saying 744 though

Answer 32

i kept the decimal where it was given and put 10^-9m

Answer 33

which is what a nanometer equals

Answer 34

oh ok

Answer 35

ok give me a few
i'm thinking