PreModule Question 30

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Sunjum Singh 1I
Posts: 30
Joined: Fri Apr 06, 2018 11:05 am

PreModule Question 30

Postby Sunjum Singh 1I » Tue Apr 24, 2018 5:18 pm

How do you go about solving this? I'm having a hard time deciphering problems like these and figuring out the first steps to solving this problem.
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Kuldeep Gill 1H
Posts: 44
Joined: Fri Apr 06, 2018 11:02 am
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Re: PreModule Question 30

Postby Kuldeep Gill 1H » Tue Apr 24, 2018 6:05 pm

Hi so what I did was a drew a picture first and labeled all the corresponding parts with what I knew. I think starting with a picture definitely helps you figure out where to begin and what is actually happening. So for A, we are told 3.607*10^-19 J is REQUIRED to remove an electron so since it says that this is the energy required to remove an electron we can conclude that this is the threshold energy or the work function. The question also tells us there is zero kinetic energy and we know that when the energy of the incoming light is equal to the threshold energy that's when we get an ejected electron with zero kinetic energy. So now plug in the energy into
lambda=(c*h)/E and that will give you the longest wavelength that would eject an electron while still having zero kinetic energy.

In 31 B. they tell you the kinetic energy and they ask for the energy of the incident(incoming) light since we already know the threshold energy (given above) you plug in the energies into E(photon)= threshold + KE and solve for E(photon) this will give you the energy of the incident light then taking the energy of the photon plug it into lambda=(c*h)/E and this will give you the wavelength of the incident light.
Hope that helps!!


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