HW Question 1.27 (6th edition)

$c=\lambda v$

Shreya Tamatam 3B
Posts: 30
Joined: Fri Sep 28, 2018 12:25 am

HW Question 1.27 (6th edition)

The question asks "A lamp rated at 32 W (1W=1J.s^-1) emits violet light of wavelength 420 nm. How many photons of violet light does the lamp generate in 2 s? How many moles of photons are emitted in that time interval?"

To solve this, do we just use the given information and the formula E=hv to solve for frequency? How do we go from there and how do we use the time interval given to do so?

105114680
Posts: 60
Joined: Fri Sep 28, 2018 12:23 am

Re: HW Question 1.27 (6th edition)

The question states that the lamp is rated 32W meaning 32J of energy are emitted every second. In 2 seconds 64 J of energy would be emitted by the lamp. Solve for the frequency using the speed of light and lambda and then use the frequency in the formula E=hv to calculate the energy per photon. Since there is 64 J of energy emitted in 2 seconds, you would divide 64 by the energy per photon to determine how many photons are emitted in the 2 seconds. Then divide that number by Avogadro's number to get how many mols of photons in the 2 second interval (since photon to atom interactions are 1:1). Hope this helps!