## Problem 1.23

$c=\lambda v$

Krisdylle Repollo 4H
Posts: 33
Joined: Fri Sep 28, 2018 12:28 am

### Problem 1.23

1.23 The ray photons emitted by the nuclear decay of a technetium-99 atom used in radio pharmaceuticals have an energy of 140.511 keV. Calculate the wavelength of these rays.

During the lecture, Professor Lavelle gave us Planck's constant as h= 6.63 x 10-34 Js. But the solutions manual uses the numbers 6.62608 x 10-34 Js. I'm having trouble determining which number we input into the equation.

Does anyone know if Professor Lavelle specified which number we should use when calculating wavelength? (Do we use 6.63 or the textbook version 6.62608?)

Melody Zhang 3L
Posts: 35
Joined: Fri Sep 28, 2018 12:21 am

### Re: Problem 1.23

The reason the textbook used the 6.62608 x 10-34 Js was to match the number of sigfigs given (140.511 keV). If the given number has less sigfigs, I believe you can use 6.63 x 10-34 Js.

Sophie Roberts 1E
Posts: 61
Joined: Fri Sep 28, 2018 12:17 am

### Re: Problem 1.23

As Melody said, I believe the book used the more exact number to match the number of sig figs in the data provided, and also it is helpful to use the more exact number instead of rounding to get a more precise calculation. However, since Lavelle noted 6.626 and most resources note Planck's constant as so, I think it is fine to use this rounded version, unless you are trying to match the sig figs or get a more precise calculation.