Calculating Energy of a 701nm Photon

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To calculate the energy of a photon with a wavelength of 701 nm, the formula E = hc/λ is used, where h is Planck's constant and c is the speed of light. The wavelength must be converted to meters, resulting in 701e-9 m. The calculated energy is initially found to be 2.83e-19 J, but it is important to include units in the final answer. The key correction noted is that the energy should be expressed as a negative value because the photon is emitted. The final correct answer is -2.84e-19 J.
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Homework Statement



An excited atom emits a photon of red light with a wavelength of 701. nm, what is the energy of the photon?----> _________________J


Homework Equations



and for this, my application was

firstly get landa from formula of c=landa * nu

and then landa * h, which is Planck's constant which is 6.626e-34.

since my wavelength is 701 nm, it can be 701e-9 in order to change to meter format.

so my final application would be {(2.998e8m/s)/(701e-9m)} * ( 6.626e-34J*s)= 2.83e-19 (after rounding up to get significant figures which is 3 digits from 701nm)



The Attempt at a Solution



2.83e-19
 
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1. Units! 2.83e-19 even if it's correct numerically is still wrong. You *need* to always have units.

2. Stay in symbols! Write down E = \frac{hc}{\lambda}, then just substitute in the numbers, after conversion to correct units.

(Btw, it's "lambda" not "landa")
 
i did put J (unit) at the end as well and it kept telling me wrong. did i do any conversion wrong?
 
oh, i got it.
the answer needed to be negetive because the question says "emits". so answer had to be negative. i replaced the answer with -2.84e-19 and it was correct. thank you for the help. now i can go to bed.
 
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