## Sapling Homework week 2 problem 5

$c=\lambda v$

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Lucy Weaver 1K
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Joined: Wed Sep 30, 2020 9:56 pm

### Sapling Homework week 2 problem 5

HI! I'm having a lot of trouble solving the 5th problem on sapling.

I muplipled planks constant by the speed of light, got 1.98644582 × 10-25 m3 kg / s2, then divided that by 9.33 * 10^-4 to get E. I found that E= 2.13 *10^-22.Then I divided that by 100 to turn it from centimeters to meters. I got 2.13*10^-24. Then I divided 51.5/2.13*10^-24 and it is giving me an incorrect.

I am not sure what I'm doing wrong, so if someone is able to help me understand that would be great!
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Lucy Wang 2J
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### Re: Sapling Homework week 2 problem 5

Hey! I think you are doing it correct but you just need to convert from cm to m before you find Energy (J).

HannahRobinson3L
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### Re: Sapling Homework week 2 problem 5

Hi! I think you have to convert the wavelengths from cm to meters before you calculate the energy, or else you end up with a different answer. If you convert the wavelength first, you should get an energy of 2.13*10-20. Hope this helps.

Margia Adriano 2A
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Joined: Wed Sep 30, 2020 10:00 pm

### Re: Sapling Homework week 2 problem 5

Hi! I think you should try (Planck's constant)(speed of light)/(9.33*10^-6) instead of (Planck's constant)(speed of light)/(9.33*10^-4). When you divide the latter by 100 instead of doing it like the former equation, I believe you get different answers. Hope this helps! If I'm wrong, please correct me!

Emma Strassner 1J
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### Re: Sapling Homework week 2 problem 5

HannahRobinson2L wrote:Hi! I think you have to convert the wavelengths from cm to meters before you calculate the energy, or else you end up with a different answer. If you convert the wavelength first, you should get an energy of 2.13*10-20. Hope this helps.

Hi, I agree with this. Converting from cm to meters first is necessary to get the right answer for E. If you wait until after you won't be converting the right units, which is why you would get the wrong answer.

idella 1D
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### Re: Sapling Homework week 2 problem 5

Where do you get the 9.33x10^-6 from?

Melanie Lin 3E
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### Re: Sapling Homework week 2 problem 5

idella 1F wrote:Where do you get the 9.33x10^-6 from?

Hi Idella! The problem said that the wavelength was 9.33x10^-4 cm so you have to convert it to meters before plugging it into the E=hc/wavelength. In meters, the wavelength would be 9.33x10^-6.

idella 1D
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Joined: Wed Sep 30, 2020 9:51 pm

### Re: Sapling Homework week 2 problem 5

Melanie Lin 3B wrote:
idella 1F wrote:Where do you get the 9.33x10^-6 from?

Hi Idella! The problem said that the wavelength was 9.33x10^-4 cm so you have to convert it to meters before plugging it into the E=hc/wavelength. In meters, the wavelength would be 9.33x10^-6.

thank you! i really appreciate it :')

AlyssaMaynard1C
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Joined: Fri Mar 06, 2020 12:15 am

### Re: Sapling Homework week 2 problem 5

Margia Adriano 3C wrote:Hi! I think you should try (Planck's constant)(speed of light)/(9.33*10^-6) instead of (Planck's constant)(speed of light)/(9.33*10^-4). When you divide the latter by 100 instead of doing it like the former equation, I believe you get different answers. Hope this helps! If I'm wrong, please correct me!

Where is the 9.33*10^6 coming from?

AlyssaMaynard1C
Posts: 60
Joined: Fri Mar 06, 2020 12:15 am

### Re: Sapling Homework week 2 problem 5

Melanie Lin 3B wrote:
idella 1F wrote:Where do you get the 9.33x10^-6 from?

Hi Idella! The problem said that the wavelength was 9.33x10^-4 cm so you have to convert it to meters before plugging it into the E=hc/wavelength. In meters, the wavelength would be 9.33x10^-6.

I'm seeing the wavelength as 851nm on the question

Juliana Rosales 1H
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Joined: Wed Sep 30, 2020 9:43 pm

### Re: Sapling Homework week 2 problem 5

I had trouble with this one too! Lol

Juliana Rosales 1H
Posts: 72
Joined: Wed Sep 30, 2020 9:43 pm

### Re: Sapling Homework week 2 problem 5

I had trouble with this one too! Lol

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