## HW #1.7

$c=\lambda v$

Jamie Reniva 1J
Posts: 14
Joined: Wed Nov 15, 2017 3:00 am

### HW #1.7

For homework problem 1.7 letter (A), it gave frequency (v) and the constant is already known (c). We can find the wavelength through this way but it is asking for the final answer in nanometers, what steps do we take to convert the current answer into to nanometers?

Question from the textbook:
"(a) The frequency of violet light is 7.1 1014 Hz. What
is the wavelength (in nanometers) of violet light? (b) When an electron beam strikes a block of copper, x-rays with a frequency of 2.0 1018 Hz are emitted. What is the wavelength (in picometers) of these x-rays?"

Andrew Evans - 1G
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Joined: Fri Apr 06, 2018 11:02 am
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### Re: HW #1.7

Once you have the wavelength in the standard SI unit (meters), you just have to use dimensional analysis to convert it to nanometers or picometers:

_____ m * (10^9 nm / 1 m) = ______ nm

_____ m * (10^12 pm / 1 m) = _______ pm

.... since there are 10^9 nanometers in every meter and 10^12 picometers in every meter.

–Andrew Evans
Section 1G

Posts: 41
Joined: Wed Nov 15, 2017 3:01 am

### Re: HW #1.7

I'm still having trouble with the conversion part of the question. Can anyone show me the steps for the conversion?

SammiOrsini_1B
Posts: 45
Joined: Fri Apr 06, 2018 11:04 am

### Re: HW #1.7

I think i am a little confused too. I thought there were 10^-9 meters in a nanometer and 10^-12 meters in picometer.

Aman Sankineni 2L
Posts: 103
Joined: Fri Aug 30, 2019 12:17 am

### Re: HW #1.7

SammiOrsini_1B wrote:I think i am a little confused too. I thought there were 10^-9 meters in a nanometer and 10^-12 meters in picometer.

This should be right. Use dimensional analysis with these numbers in order to convert from meters to nanometers/picometers.

Cynthia Rodas 4H
Posts: 51
Joined: Wed Sep 18, 2019 12:21 am

### Re: HW #1.7

Part a:
So in order to convert the answer from meters to nanometers, you would try to cancel out the meters in order to get nm by itself. For example:
$(4.22 * 10^{-7} m) * (\frac{1 nm}{10^{-9} m})$
This would leave the result as 422 nm.

Part b:
This follows the same concept as Part a, only it would be:
$(1.5 * 10^{-10} m) * (\frac{1 pm}{10^{-12} m})$
which would give you 150 pm.