Mubashira – Satawa
Review of Literature
Light intensity is a very important factor when dealing with stage lights.
Light intensity is how light spreads out over a certain area at a given distance.
Ultimately, it decides how bright the area will be. There are many factors related
to light intensity and many more that could affect it.
To start, readers must know about the electromagnetic spectrum. The
electromagnetic spectrum, or EM spectrum, is the range of frequencies of
different wavelengths. The researchers will focus on the visible light section of
the EM spectrum. As Gunderson stated in The Handy Physics Answer Book,
"visible light ranges from 4*1014 Hz to 7.9*1014 Hz." In other terms, the visible
light spectrum ranges from "700 nanometers (abbreviated nm) to approximately
400 nm" (Henderson).The visible light spectrum starts at red and goes up to
violet. Refer to figure 1 below to see the visible light spectrum. Each color has a
certain wavelength that is created by photons. The wavelengths are measured
from crest to crest or trough to trough of the wavelength. The red wavelengths
are longer and the violet wavelengths are shorter. The visible light spectrum is
set up in order of low to high frequency. This means red has the lowest
frequency in the visible light spectrum while violet has the highest frequency as
stated in Irving Alder's Color In Your Life (15).
Figure 1. The Visible Light Spectrum (Light Basics)
Mubashira – Satawa
Light "waves carry energy" (Light Basics). The shorter wavelengths carry
more photons so they have more energy. The more energy there is, the higher
the frequency, thus having a greater intensity. The colors closer to violet on the
visible light spectrum have shorter wavelengths so they should have higher
intensity than the colors closer to red (McMilla1 n). However, this does not hold
true when white light is changed to a different color using gel colors. When a blue
gel color was used on the stage light, the gel color only let blue photons through.
The other colors were not let through the gel. Since there were less photons
being allowed through the gel, there was less energy going through. Because of
this, the intensity decreased. Contrastingly, when a pink gel was used, there
were more photons that went through the gel. The only photons that were not let
through were blue, violet, and possibly green. There was more energy so the
pink light created by the pink gel would have a higher intensity than the blue light.
White light is different, though. White light consists of all the colors so none of the
photons are being blocked. All the photons are allowed to pass since there is no
gel for white light. Therefore, white light had the highest intensity.
The next thing to understand is light intensity. Light intensity is perceived
as brightness. Intensity is the rate that light spreads over a certain surface at a
certain distance from a source. Henderson has stated and explained that
distance will have an effect on the intensity. As the distance between the light
source and object increases, the distance between the light rays increases so it
shines on a larger area.
Mubashira – Satawa
Light intensity is measured in lux, which is one lumen per square meter. A
lumen is the total amount of visible light that is present. Lux measures the total
amount of light that is shined on something per unit area.
PASCO and Australia School of Innovation in Science, Technology, and
Mathematics (ASISTM) have done experiments relating to this topic. Both
experiments investigated the relationship between light intensity and the distance
from a light source. The experiments tested the level of light intensity at different
distances between the light source and the Lux meter or similar sensor. Their
results showed that lux decreased as distance increased. The PASCO lab was
more complicated than the ASISTM lab, but both tested relevant factors.
These experiments test distance like the researchers did in their
experiment. The researchers used the information to found by these experiments
to help with their hypothesis. They learned that the closest distances would
create the highest amount of lux. The researchers used the information found
about the wavelengths and how gel color affects it to help with creating the
hypothesis as well. This information backs up the claims the researchers made
and their hypothesis. One factor that was not found was how the angling of the
stage light affects intensity. The researchers tested a variable that had not been
tested before.
Mubashira – Satawa
Works Cited
Adler, Irving. Color in Your Life. New York: John Day, 1962. Print.
ASISTM. Light Intensity Experiment. Synchrotron Investigations. The University
of Western Australia, n.d. Web. 18 Apr. 2013.
<http://asistm.duit.uwa.edu.au/synchrotron/downloads/pdfs/chapter09_7.p
df>.
Gundersen, P. Erik. "Light." The Handy Physics Answer Book. Detroit, MI: Visible
Ink, 1999. 233-84. Print.
Henderson, Tom. "The Electromagnetic and Visible Spectra." The
Electromagnetic and Visible Spectra. The Physics Classroom, n.d. Web.
15 Apr. 2013. <http://www.physicsclassroom.com/Class/light/u12l2a.cfm>.
Henderson, Tom. "Light Intensity." The Physics Classroom. The Physics
Classroom, n.d. Web. 15 Apr. 2013.
<http://www.physicsclassroom.com/reasoning/light/src35.pdf>.
Henderson, Tom. The Visible Light Spectrum. Digital image. The Physics
Classroom. The Physics Classroom, n.d. Web. 15 Apr. 2013.
<http://www.physicsclassroom.com/Class/light/u12l2a2.gif>.
"Illuminance - Recommended Light Levels." Illuminance - Recommended Light
Levels. The Engineering Toolbox, n.d. Web. 18 Apr. 2013.
<http://www.engineeringtoolbox.com/light-level-rooms-d_708.html>.
Mubashira – Satawa
"Light Intensity." Light Intensity. The Regents of the University of California, n.d.
Web. 15 Apr. 2013.
<http://cse.ssl.berkeley.edu/segwayed/lessons/light/measure3.html>.
McMillan, Greg. Personal Interview. 18 Apr. 2013.
PASCO. Light Intensity vs. Distance (Light Sensor, Rotary Motion Sensor).
PASCO, n.d. Web. 18 Apr. 2013.
<http://kwcweb.kwc.edu/depts/math/johnsonb_courses/Physics_1302_Su
mmer/HandsOn_Physics_Activities/61_Intensity_Vs_Distance.pdf>.