## Sapling Week 2-4 HW Question 1

$c=\lambda v$

Vivian Leung 1C
Posts: 221
Joined: Wed Sep 30, 2020 10:09 pm

### Sapling Week 2-4 HW Question 1

Hi!

Does anyone know how to explain the answer to this problem:

Consider a single photon with a wavelength of "lambda", a frequency of v, and an energy of E.

What is the wavelength, frequency, and energy of a pulse of light containing 100 of these photons?

Micaela Estavillo
Posts: 55
Joined: Wed Sep 30, 2020 9:44 pm

### Re: Sapling Week 2-4 HW Question 1

The wavelength & the frequency of the 100 photons are the same as the single-photon since the pulse of light contains 100 times the single-photon. This means for the pulse of light...
the wavelength is λ
the frequency is ν
the energy is 100E (100 times the E of the single photon)

Keon Amirazodi 3H
Posts: 95
Joined: Wed Sep 30, 2020 9:59 pm

### Re: Sapling Week 2-4 HW Question 1

Each photon of light adds to the overall energy. So with 100 photons, the energy would be multiplied by 100. However, wavelength and frequency is a set property of the photon which means it wouldn't change with the number of photons.

Arnav Saud 2C
Posts: 117
Joined: Wed Sep 30, 2020 9:51 pm

### Re: Sapling Week 2-4 HW Question 1

Energy of light is proportional to the number of photons, which means that E= 100. (This could be interpreted as the intensity of the light if I'm correct)
Wavelength and frequency are set properties which means that each photon in a pulse will have the same frequency.
This means that the wavelength is just λ and the frequency is just v.

Dylan_Nguyen_2C
Posts: 87
Joined: Wed Sep 30, 2020 9:41 pm

### Re: Sapling Week 2-4 HW Question 1

The way I thought about this one is that the amount of photons does not change the pulse's wavelength or frequency, but does affect the intensity or overall energy of the pulse of light. Therefore the wavelength λ stays the same, as does the frequency v; however the energy E(which can be thought of as the intensity of the light) will increase proportionally to the amount of photons in the pulse of light, making the energy value 100*E.

rhettfarmer-3H
Posts: 101
Joined: Wed Sep 30, 2020 9:59 pm

### Re: Sapling Week 2-4 HW Question 1

This question is very conceptual. The wave length and the frequency are both properties of light so no matter the number of photons this number is not going to change whether there are a thousand or million or one. This is the same idea that was presented on the phoetonic effect when they increased the intensity. Increasing intensity or more photons will add to Energy so it would be 100E. but the rest stays the same.

Fernanda Olvera 3D
Posts: 50
Joined: Wed Sep 30, 2020 9:41 pm

### Re: Sapling Week 2-4 HW Question 1

I agree with Micaela,
To my understanding, measurable properties of the pulse of light are both the wavelength & frequency.

Vivian Leung 1C
Posts: 221
Joined: Wed Sep 30, 2020 10:09 pm

### Re: Sapling Week 2-4 HW Question 1

Thank you everyone! That makes a lot of sense.

Posts: 98
Joined: Wed Sep 30, 2020 9:51 pm

### Re: Sapling Week 2-4 HW Question 1

So, electromagnetic energy is measured in units of photons. Wavelength and frequency are set properties of the pulse of light, and energy is proportional to the number of photons.

So because the question is asking for the energy of 100 photons, the answer would be energy, E, is 100, along with just wavelength and frequency being just the symbols.