PHYSICS AND THE VISUAL ARTS
Notes on LAB 6
THE VISIBLE SPECTRUM
Activity 1. Part 3.
You may have some difficulty with the spectroscope if your eyes will not focus on the scale. You can get an estimate
of the wavelength of your laser by shining the laser on a piece of white paper and holding the spectroscope so that
you can see the reflected laser light throug the slit. Do not look directly at the laser with the
spectroscope!
Prefixes and Scientific Notation
In physics we frequently encounter number that are very large or very small. Examples include the speed of light
(very large) and the wavelength of light (very small). Such numbers are most easily express by the use of
scientific notation, which uses powers of 10. This notation provides an easier way of writing large and small
numbers and of doing arithmetic with them. To illustrate, note that we may write the number "one thousand" in the
following way:
1000 = 10x10x10 = 103.
With this notation, we can conveniently express very large or very small numbers. For example,
127,000,000 = 1.27 x 100,000,000 = 1.27 x 108
and
0.00037 = 3.7 x 0.0001 = 3.7 x 10-4.
Using the scientific notation, 1670 meters can be written as 1.67 x 103 meters. But this same quantity can
also be written as 1.67 kilometers - abbreviated as 1.67 km. This is an example of using a prefix to indicate a
decimal multiple of a base unit. Here the prefix kilo means one thousand or 103. The table below gives the
prefixes for other multiples or submultiples of units. We have already used the prefix "nano" in giving the
wavelengths of light. Nano stands for 10-9.
Numbers expressed in scientific notation may be multiplied and divided according to the usual rules of algebra.
Remember that
10n x 10m = 10n+m and
10a/10b = 10a-b.
When using numbers with prefixes, they should be converted to scientific notation in the proper units before being
used in calculations.
When entering scientific numbers into the LONCAPA you do not write out the 10 with the exponent. Rather a number like
the speed of light, 3.0 x 108 m/s, would be entered as: 3.0E8 m/s. If your number and units are correct,
it will be accepted by the computer. If units are called for and you submit a number without units, the computer will
prompt you to include them. The computer does recognize units with prefixes such as nm, mm, Mm, etc.
SI Prefixes
| Factor | Prefix | Symbol |
|---|
| 109 | giga | G |
| 106 | mega | M |
| 103 | kilo | k |
| 10-2 | centi | c |
| 10-3 | milli | m |
| 10-6 | micro | μ |
| 10-9 | nano | n |
| 10-12 | pico | p |
Note that all of the prefix symbols for small numbers (i.e., negative exponents) are lower case letters. All of the
symbols for large numbers (positive exponents) are upper case letters with the sole exception being the k for
kilo.
Submitting your report.
In this DVD lesson you saw what we call "line spectra." In the summary you are asked to compare what your eyes see
with what the TV system reproduces. To remind yourself what you have already seen of a continuous spectrum on the TV,
go back to the DVD for Lesson 1 where the continuous spectrum was shown. Then you can make the proper comparisons.
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Last Modified: 07/14/11
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