Question

16) How many photons are contained in a burst of yellow light (589 nm) from a sodium lamp that contains 609 kJ of energy?

Answer 1

The correct answer to this question is this one:

find the energy of one photon:

E=h*c/λ

divide the energy given by the energy of one photon of that wavelength

What I've done so far is convert wave length to m and energy to j. 

E photon = h * x / wave length
E = (6.626 x 10^-43)(3.00 x 10^8) / 587 ^ -9  = 3.38 x 10 ^18 J
3.38 x 10 ^18 J x 1000 kj / 1 j = 3.37 x 10 ^ 16 Kj
609 kJ/  3.37 x 10 ^ 16 Kj =  1.81 x 10 ^ 16

E = (6.626 x 10^-34)(3.00 x 10^8) / 587 ^ -9 = 3.38 x 10 ^19 J
3.38 x 10 ^19 J x 1000 kj / 1 j = 3.37 x 10 ^ -16 Kj
609 kJ/ 3.37 x 10 ^ 16 Kj = 1.81 x 10 ^ 18 but the answer is  1.81 × 10^24 photons

3.38 x 10 ^-19 J
should be negative

then 3.38 x 10 ^18 J x 1kJ/1000 J

you're converting from J to kJ.. just like meters to kilometres, you wouldn't multiply you would divide

Answer 2

Answer:  C) $1.81\times 10^{24}$ photons

Explanation:

$E=\frac{nhc}{\lambda}$

E= energy = 609 kJ = 609000 J    (1kJ=1000J)

$n$ = number of photons = ?

h = Planck's constant  = $6.626\times 10^{-34}Js$

c = speed of light = $3\times 10^8m/s$

$\lambda$ = wavelength of photon = 589 nm =$589\times 10^{-9}m$

Putting values in above equation, we get:

$609000J=\frac{n\times (6.626\times 10^{-34}Js)\times (3\times 10^8m/s)}{589\times 10^{-9}m}$

$n=1.81\times 10^{24}$

Thus there are $1.81\times 10^{24}$ photons in a burst of yellow light (589 nm) from a sodium lamp that contains 609 kJ of energy.