This is my Laboratory Blog. It consists of the different Engineering Physics Labs that I have done in class over the duration of the Spring 2013 Semester at Mt. San Antonio College :)
Purpose: to measure the thickness of human hair using a laser and a micrometer in order to compare the two different methods of measureming.
Equipment:
Notecard
Human hair
Tape
Lazer
Meter stick
Experiment:
A hole was punched into a notecard, for which a human hair from a classmate was then taped across the diameter of the small perfuration.
In a darkened classroom, the red lazer was turned on, turning the thickness of the hair into a slit to cause a diffraction pattern as observed bellow.
The distance from which the hair was positioned was measured to be ~1meter as displayed bellow
The diffraction pattern was then physically drawn onto the white board suface for further measurements with the classroom light on. This allowed us to visualize the distance between minima as shown in the next image.
Conclusion:
It was determined that the experimental method of using a lazer to measure human hair was within an acceptable range of value after calculating the uncertainty of its diameter based on the average diameter for black hair.
Purpose: To observe some of the characteristics of a converging lens when the object is placed on one side of the lens and the real inverted image is placed on the other side of the lens.
Equipment:
Convergering lens
Light box with outline image
Meter stick
12 inch ruler
Lens holder
White board
Experiment:
Light Box with outline image to be projected
Physical Set up of the experiment
In the experiment we determined the focal length of the lens by using a
simple visual analysis and measurement.
A focal point distance from the surface to lens was measured by holding the lens horizontally above a lamp until the light was maximized using a 12 inch ruler.
f = 5.2 ±0.5 c.m
The lens was then clamped onto a holder, and set at a distance of 1.5f, 2f,
3f, 4f, and 5f and fixed at an object height for the experiment.
This resulted in different image distance and image heights.
Table 1: Measured Data
The uncertainty was calculated using the max/min values for Magnification calcuation. And bellow is a sample calculation.
At an object distance of 0.5f, the image was completely blurred and it bacame virtual, as shown in the image bellow
As shown in the picture above, it is completely viewable inside the lens itself.
Conclusion:
In plotting the inverse image distance vs. negative inverse object distance yileded a linear relationship confirming a correct initial focal length.
Purpose: To explore the images formed by convex and concave
mirrors through direct observations and light ray
diagrams
Equipment:
Convex mirror
Concave mirror
Worksheets at the end of lab activity packet
Ruler
Object(myself)
Experiment:
Part A
- Convex Mirror
Far Away from Convex Mirror
From the direct observations, a convex mirror will make an object appear smaller
than the same size object from a far distance. This object remains upright.
Clore up to Convex Mirror
As the object is brought close up to the convex mirror, the image appears larger
than the same size real object.
From a farther distance than the
first picture, the image appears to be so far it disappears.
Part B -
Concave Mirrors
Close up to Concave Mirror
As the object(me) got closer to the mirror, the image became bigger and remained upright.
Close up to Concave Mirror
As the object was much further away, the mirror image was much smaller and inverted, as depicted in the picture above.
Conclusion:
Based on the light ray sketches, bellow of a convex and concave mirror respectively, we can conclude that the observations and calculations match based on the magnification value.
Purpose: To use the geometry of a semicircle to analyze the properties of reflection and refraction when an electromagnetic wave travels through a medium of a different material.
Equipment:
Light box
Semicircular plastic
Circular protractor
Experiment:
A beam of light was emited from a light box position at a known angle onto the circular protractor.
The refracted wave will have a different angle than the angle of incidence, normal to the surface of the semicircular plastic.
Through visual analysis, a difference can be recorded using the opposite side of the circular protractor. Increasing increments of 5-8 degrees will be used for a total of 10 trials.
Prism A - Incidence Ray onto circular side
Data Collected for Set up Demostratrated Above - Part A
Prism B - Incidence Ray onto flat side
Data Collected for Set up Demostrated Above - Part B
Conclusion:
Part A)
The light ray on the onto the curved surface of the semicircular prism was reflected as predicted. The Linear regression line and slope of sinÓ¨1 vs sinÓ¨2 represent the n(air)/n(glass).
This makes sense since the index of refraction of the prism is greater than air(1.00), therefore the slope being less than 1 confirms the relationship of the difraction in the prism.
Part B)
Re-enforceably, the results were once again attained from the reversed physical set up of the prism. The slope from the linear regression line was the same, comfirming the same index of refraction of the prism.
Purpose: To use a simple antenna made from a short piece of metal to analyze the behavior of electromagnetic radiation.
Equipment:
Copper Wire
Two Meter Sticks
BNC Connector
Frequency Generator
Oscilloscope
Experiment:
Transmitter to the high frequency oscillator, with free space between the two antennae
A transmitter was created by attaching the copper wire to a meter stick with tape. Then, one end to the frequency generator was connected, this create a
receiver by having a pluggin at the BNC connector into the oscilloscope.
BNC connected
The frequency generator was used to create a frequency of 30 kHZ with the amplitude to its maximum.
Frequency generator set at 30kHz
Change the time/div setting on the
oscilloscope to 0.1 ms and decrease the voltage/div until a signal in
seen on the screen.
Oscillator set at 30kM with a max amplitude, with the oscilloscope at 0.1ms
The measurements of the peak to peak amplitude of
the EM wave were observed for several trials.
Conclusion:
The data does not fit the A/r function as it was expected if it were a
point charge due to the fact that the transmitter is linear perpendicular to the
receiver. Therefore, the entirely of the copper wire length must be taken at each dx and consider that instead of a
single point source.
The A/x
function has a better fit for the data compared to the A/r^2. Yet, the fit is still not a complete fit.
The additional A/r^n function actually fits the best.
Purpose: To use student voice produced and harmonic turning-fork sound waves to conceptualize the wave like properties of sound.
Equipment:
LabPro
Microphone
Singers(Students)
Experiment:
The experiment collected a 0.03 second recording of an "AAAAAAAA" from a students, a much more harmonic turning fork striking a soft surface.
The following questions were proposed and asked to be answered for all Parts A thru D
1)Would you say this is a
periodic wave?Support your answer with
characteristics.
2)How many waves are shown in this sample?Explain how you determined this
number.
3)Relate how long the probe collected data to
something in your everyday experience. For example: “Lunch passes by at a snails
pace.” Or “Physics class flies by as fast as a jet by the
window.”
4)What is the period of
these waves?Explain how you determined
the period.
5)What is the frequency of these waves?Explain how you determined the
frequency.
6)Calculate the wavelength assuming the speed of
sound to be 340 m/s. Relate the length of the sound wave to something in the
class room.
7)What is the amplitude of
these waves?Explain how you determined
amplitude.
8)What would be different about the graph if the
sample were 10 times as long? How would your answers for the questions a-g
change? Explain your thinking. Change the sample rate and test your ideas. Copy
the graph and label it #1h.
Part B Specific:
Have someone else speak
into the microphone and compare and contrast the two graphs.
Part C Specific:
Then use a
tuning fork to produce a graph and compare and contrast that graph against the
human graphs.
Part D Specific:
What would you expect if the tuning fork wasn't as loud
as the first time?
Conclusion: Part A:
"My beutiful Voice" by Jose Comi
1)This wave is periodic since it repeats similar
to a sinusoidal wave.
2)5.4 waves are in this sample.
3)The data was collected over 0.03 seconds which
is faster than you blink.
4)The period of the wave is 0.0056 seconds.We determined this by dividing the sample
time (0.03) by the number of waves (5.4).
5)The frequency is 180 Hz.We determined this by 1/T and confirmed it by
extrapolating 5.4 waves in .03 seconds and looked at how many waves in one
second (frequency).
6)The wavelength equals velocity divided by the
frequency.(340m/s) / (180 s-1)
= 1.89m.This is about the length of a desk.
7)The amplitude is 1.8 units.We determined this from the graph.
8)Everything would be the same except you would
have more waves in the sample.
Part B:
"The sound of aerospace" - Jason Shaw
1)The second wave sampling was not as regular as
the first.There are 3.5 waves in the
sample which is 0.03 seconds.The period
is 0.0086 seconds.The frequency of the
wave is 116 Hz.The wavelength is 2.93
m.The amplitude is 0.75 units.
Part C:
The tuning fork produces a much more uniform sound wave
compared to the human waves.There are
15 waves in the sample of 0.03 seconds.The period is 0.0020 seconds.The
frequency of the wave is 500 Hz.The
wavelength is 0.68 m.The amplitude is
0.23 units.
Part D:
Only the amplitude of the wave changed (decreased) while the
other data remained the same.We changed
the impact surface to a softer material (skin/pants vs rubber shoe sole) which
resulted in a softer wave.
