## HW 1.7 (using nm vs pm)

$c=\lambda v$

Maya Khoury
Posts: 29
Joined: Fri Apr 06, 2018 11:03 am

### HW 1.7 (using nm vs pm)

For problem 1.5, why does the answer manual show that part a is answered in nanometers but part b is answered in picometers? And how would I know when to use which?

Jesus A Cuevas - 1E
Posts: 29
Joined: Fri Apr 06, 2018 11:02 am

### Re: HW 1.7 (using nm vs pm)

When it comes to the use of the short hands, it is determined by what power of 10 our answer is raised to. For this question, in part (a) it specifically asked for nanometers (10^-9) and in part (b) it asked for the answer in picometers (10^ -12). We will usually be told what units the final answer should be in, if not we assume its the units that correspond closest to what power of 10 our answer is raised to (ex: Gigameter 10^9, Kilometers 10^3, Decimeters 10^ -1, etc.).

ramayyala1G
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Joined: Fri Feb 02, 2018 3:02 am

### Re: HW 1.7 (using nm vs pm)

Adding on to that, unless the specify what type of unit they want you to use, I am pretty sure you are free to choose then. Its usually best to stick with the units given in the problem unless told otherwise.

FizaBaloch1J
Posts: 41
Joined: Fri Apr 06, 2018 11:01 am

### Re: HW 1.7 (using nm vs pm)

Had a question regarding example 3 in chapter 1 as well?

Which of the following happens when the frequency
of electromagnetic radiation decreases? Explain your
reasoning.
(a) The speed of the radiation decreases.
(b) The wavelength of the radiation decreases.
(c) The extent of the change in the electrical fi eld at a given
point decreases.
(d) The energy of the radiation increases.

Chem_Mod
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### Re: HW 1.7 (using nm vs pm)

Please post full details of the question if you want to ask a question about the book questions so everyone can understand without having to open the book.

Neha Divi 1K
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Joined: Fri Apr 06, 2018 11:02 am

### Re: HW 1.7 (using nm vs pm)

I agree with what everyone else said. In addition, I think the answer was trying to show the value without scientific notation and in terms that would help you understand the scope of the problem and compare that to the answer and its units.

Andrew Berard 1F
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Joined: Fri Apr 06, 2018 11:01 am

### Re: HW 1.7 (using nm vs pm)

Haison Nguyen 1I
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Joined: Fri Apr 06, 2018 11:04 am

### Re: HW 1.7 (using nm vs pm)

The problem itself says to use nm for part A and pm for part B. If the problem didn't tell you what units to use, you should probably use the units you were working with to solve the problem.

Bijal Luhar
Posts: 33
Joined: Fri Apr 06, 2018 11:03 am

### Re: HW 1.7 (using nm vs pm)

The units the question asks for does not ultimately change the ultimate answer, it is just a specification they have.