Question

A mole of red photons of wavelength 725 nm has ________ kj of energy.

Answer 1

According to the general rules and basic knowledge of physics, without any doubds I can say that a mole of red photons of wavelength 725 nm has  [D] 165 kj of energy. I converted  a wavelength into energy in that way : 
$(E)= 6.023 x 10 ^23 x 6.625 x 10 ^ -34 x3 x 10^8/725x10^-9$=$=0.1651 x10 ^ 6 J = 165 Kj.$

Answer 2

Answer:

The energy of red photons of this particular wavelength is 2.7399×10^-22 kj

Explanation:

You can do this in two ways.

The first will be using the energy of a photon's expression:

E= hc/λ

where h is Planck's constant, c is the speed of light and λ is the photon's wavelength. Therefore,

E= (6.626×10⁻³⁴)(299792458)/(725×10⁻⁹)

E=2.7399×10⁻¹⁹ J

To get the answer to be in kilo-joules, we divide the answer above by 1000. Therefore, we get the final answer to be

E=(2.7399×10⁻¹⁹)/1000

E=2.7399×10⁻²² kj

The second way that you can calculate the energy of red photons is by using the expression

E=hf

where h is Planck's constant and f is the frequency of the photons.

When using this method, we first need to determine the frequency of the photons and this is done by using the expression

f=c/λ

where c is the speed of light constant and λ is the wavelength of the photons. Therefore,

f=299792458/725×10⁻⁹

f=4.135×10¹⁴ J/s

After determining the frequency, we can calculate the energy by using the expression

E=hf. Thus

E=(6.626×10⁻³⁴)(4.135×10¹⁴)

E=2.7399×10⁻¹⁹ J

To get the answer to be in kilo-joules, we divide the answer above by 1000. Therefore, we get the final answer to be

E=(2.7399×10⁻¹⁹)/1000

E=2.7399×10⁻²² kj