PHYSICS 3LC FINAL EXAM REVIEW
COMPLETE QUESTIONS WITH CORRECT
ANSWERS
\.What does a photometer do? - ANSWERS✔-It converts light into electric current.
\.What are photons? - ANSWERS✔-Tiny quantized packets of light.
\.What happens in the photoelectric effect? - ANSWERS✔-Light hits a metal and
electrons are emitted.
\.What should the digital multimeter be set to read? - ANSWERS✔-Voltage
\.Which of the following DOES NOT describe projection imaging? - ANSWERS✔-
Produces images of selected planes or slices of tissue of the patient's body.
\.Which of the following DOES NOT describe tomographic imaging? - ANSWERS✔-
A large volume of the patient's body can be viewed with one image.
\.An ordinary dental X-ray uses which imaging technique(s)? - ANSWERS✔-
Projection
,\.Which of the following is NOT a requirement for a suitable probe beam? -
ANSWERS✔-It interacts with a large number of cells
\.Some wave energy can penetrate and pass through a sample. This is a
description of what type of interaction with matter? - ANSWERS✔-Transmission
\.Which of the following is true for the reflection coefficient for a perfect mirror? -
ANSWERS✔-I_r / I_o = 1
\.How does the flux of light from an isotropic source depend on the distance r
from the source? - ANSWERS✔-r^-2
\.What factors DO NOT affect visual acuity? - ANSWERS✔-- Region of retina image
falls upon
- Density of receptors
- Level of illumination
All of the above factors affect visual acuity
\.Where does the actual 'weld' take place on the retinal, based upon the
physiology of the eye? - ANSWERS✔-Pigmented Epithelium
\.Why is damage to neighboring tissue minimized?
,(in the context of using cauterizing instruments and lasers for medical procedures)
- ANSWERS✔-Because the laser beam is intense and has very low divergence its
energy can be focused onto a small spot.
\.Which statement is correct?
A desk lamp is a isotropic source. A laser is an isotropic source.
A desk lamp is a collimated source. A laser is an isotropic source.
A desk lamp is a collimated source. A laser is a collimated source.
A desk lamp is an isotropic source. A laser is a collimated source.
None of the above - ANSWERS✔-A desk lamp is an isotropic source. A laser is a
collimated source.
\.How does the flux of light from an collimated source depend on the distance r
from the source? - ANSWERS✔-It is a constant independent of distance.
\.To resolve two point sources, what distribution of cones must occur where the
image strikes the retina? - ANSWERS✔-There must be a cone producing less than
the full response between two cones that produce the full response.
\.Suppose you want to take a chest X-ray with an X-ray source that has a
divergence of 5º . If the film is 1 meter from the (point) source, how big is the spot
size at the film in centimeters?
____________cm - ANSWERS✔-X ray source that has divergence of 5 degrees
= 5º(180/pi) = 0.08727 rad
, distance r = 1 m
spot size at the film is r ?
= 1.0 m * 0.08727 rad
= 0.08727 m * 100
= 8.7 cm
\.A bothersome feature of many physical measurements is the presence of a
background signal (commonly called "noise"). In Part 2.2.4 of the experiment,
some light that reflects off the apparatus or from neighboring stations strikes the
photometer even when the direct beam is blocked. In addition, due to electronic
drifts, the photometer does not generally read 0.0 mV even in a dark room. It is
necessary, therefore, to subtract off this background level from the data to obtain
a valid measurement. Suppose the measured background level is 5.1 mV. A signal
of 20.7 mV is measured at a distance of 29 mm and 15.8 mV is measured at 32.5
mm. Correct the data for background and normalize the data to the maximum
value. What is the normalized corrected value at 32.5 mm?
_________ - ANSWERS✔-Subtracting the background:
@ 29mm: 20.7 - 5.1 = 15.6 mV
@ 32.5mm: 15.8 - 5.1 = 10.7 mV
"Normalize the data to the maximum value" probably means to set the peak value
to unity and scale the remaining data by the same factor. Which means divide
everything through by 15.6 mV. (This assumes that the maximum value occurs at
32.5mm, which really has not been stated anywhere.)
So, at 32.5mm, the normalized corrected value is 10.7/15.6 = 0.6859 = 0.69
COMPLETE QUESTIONS WITH CORRECT
ANSWERS
\.What does a photometer do? - ANSWERS✔-It converts light into electric current.
\.What are photons? - ANSWERS✔-Tiny quantized packets of light.
\.What happens in the photoelectric effect? - ANSWERS✔-Light hits a metal and
electrons are emitted.
\.What should the digital multimeter be set to read? - ANSWERS✔-Voltage
\.Which of the following DOES NOT describe projection imaging? - ANSWERS✔-
Produces images of selected planes or slices of tissue of the patient's body.
\.Which of the following DOES NOT describe tomographic imaging? - ANSWERS✔-
A large volume of the patient's body can be viewed with one image.
\.An ordinary dental X-ray uses which imaging technique(s)? - ANSWERS✔-
Projection
,\.Which of the following is NOT a requirement for a suitable probe beam? -
ANSWERS✔-It interacts with a large number of cells
\.Some wave energy can penetrate and pass through a sample. This is a
description of what type of interaction with matter? - ANSWERS✔-Transmission
\.Which of the following is true for the reflection coefficient for a perfect mirror? -
ANSWERS✔-I_r / I_o = 1
\.How does the flux of light from an isotropic source depend on the distance r
from the source? - ANSWERS✔-r^-2
\.What factors DO NOT affect visual acuity? - ANSWERS✔-- Region of retina image
falls upon
- Density of receptors
- Level of illumination
All of the above factors affect visual acuity
\.Where does the actual 'weld' take place on the retinal, based upon the
physiology of the eye? - ANSWERS✔-Pigmented Epithelium
\.Why is damage to neighboring tissue minimized?
,(in the context of using cauterizing instruments and lasers for medical procedures)
- ANSWERS✔-Because the laser beam is intense and has very low divergence its
energy can be focused onto a small spot.
\.Which statement is correct?
A desk lamp is a isotropic source. A laser is an isotropic source.
A desk lamp is a collimated source. A laser is an isotropic source.
A desk lamp is a collimated source. A laser is a collimated source.
A desk lamp is an isotropic source. A laser is a collimated source.
None of the above - ANSWERS✔-A desk lamp is an isotropic source. A laser is a
collimated source.
\.How does the flux of light from an collimated source depend on the distance r
from the source? - ANSWERS✔-It is a constant independent of distance.
\.To resolve two point sources, what distribution of cones must occur where the
image strikes the retina? - ANSWERS✔-There must be a cone producing less than
the full response between two cones that produce the full response.
\.Suppose you want to take a chest X-ray with an X-ray source that has a
divergence of 5º . If the film is 1 meter from the (point) source, how big is the spot
size at the film in centimeters?
____________cm - ANSWERS✔-X ray source that has divergence of 5 degrees
= 5º(180/pi) = 0.08727 rad
, distance r = 1 m
spot size at the film is r ?
= 1.0 m * 0.08727 rad
= 0.08727 m * 100
= 8.7 cm
\.A bothersome feature of many physical measurements is the presence of a
background signal (commonly called "noise"). In Part 2.2.4 of the experiment,
some light that reflects off the apparatus or from neighboring stations strikes the
photometer even when the direct beam is blocked. In addition, due to electronic
drifts, the photometer does not generally read 0.0 mV even in a dark room. It is
necessary, therefore, to subtract off this background level from the data to obtain
a valid measurement. Suppose the measured background level is 5.1 mV. A signal
of 20.7 mV is measured at a distance of 29 mm and 15.8 mV is measured at 32.5
mm. Correct the data for background and normalize the data to the maximum
value. What is the normalized corrected value at 32.5 mm?
_________ - ANSWERS✔-Subtracting the background:
@ 29mm: 20.7 - 5.1 = 15.6 mV
@ 32.5mm: 15.8 - 5.1 = 10.7 mV
"Normalize the data to the maximum value" probably means to set the peak value
to unity and scale the remaining data by the same factor. Which means divide
everything through by 15.6 mV. (This assumes that the maximum value occurs at
32.5mm, which really has not been stated anywhere.)
So, at 32.5mm, the normalized corrected value is 10.7/15.6 = 0.6859 = 0.69
