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### 1B 15 Part C

Posted: **Wed Oct 16, 2019 12:30 pm**

by **005343842**

I am confused behind the process of part c of this question "The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 3 10 km?s . (a) What is the wavelength of the ejected electron? (b) No electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50 3 1016 Hz. How much energy is required to remove the electron from the metal surface?

(c) What is the wavelength of the radiation that caused photoejection of the electron?

The solutions says to add part B's answer with Kinetic energy but I thought it would be to subtract bc that's energy emitted?

### Re: 1B 15 Part C

Posted: **Wed Oct 16, 2019 12:38 pm**

by **Kaitlyn Ang 1J**

For part c, you're trying to calculate the incoming energy that results in the emitting of the electron and the kinetic energy it has as it zooms off with the velocity given. That means the incoming energy = work function + Ek which is why you add part b (the work function) to part a (the Ek) to get the answer to part c (the incoming energy)

And after you find the incoming energy, you can calculate the frequency and then the wavelength to get the final answer to part c

### Re: 1B 15 Part C

Posted: **Wed Oct 16, 2019 3:24 pm**

by **Drake Choi_1I**

Part A asks, "What is the wavelength of the ejected electron?" The velocity of the electron that is emitted from a metallic surface by a photon is 3.6 x 10^3 km.s^-1. Part B states no electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50x10^16 Hz. How much energy is required to remove the electron from the metal util the frequency of the radiation reaches 2.50 x 10^16 Hz. How would one go about solving part A and B?

### Re: 1B 15 Part C

Posted: **Wed Oct 16, 2019 6:30 pm**

by **Maeve Miller 1A**

In response to the comment above, for part a, you would first convert the given velocity to m/s. Then, using the λ=h/(mv) equation, (where h is Planck's constant, m is mass of the e-, and v is velocity) you will be able to find the wavelength. Remember to convert the mass into kg as well! For part b, you would plug the given frequency into the E=hv equation to solve for the energy.

### Re: 1B 15 Part C

Posted: **Sat Oct 19, 2019 12:40 pm**

by **Drake Choi_1I**

Thank you Maeve! This helped a lot.