OSH 425, Physical Agents

``` PHYSICAL AGENTS
OSH 425, HOMEWORK SET #1

1. For a sound wave with amplitude of 10 N/m2 & a frequency
of 1 KHz, calculate the maximum pressure exerted by this
wave in 20 seconds.

2. The length of a sound wave was measured to be 4.69 ft. with
a frequency of 1000 Hz.  Determine the nature of the medium
in which this wave was propagated.

3. Given 3 sources:
A with 92 dB
B with 90 dB
C with 88 dB
Calculate the following,
- Prms
- resultant SPL
- power at 50 m from source.

4. During an 8 hour shift a worker was exposed to:
90 dB for 3.5 hours
95 dB for 1 hour
85 dB for 3.5 hours
At the end of his shift the worker was complaining of noise
induced pain.  Determine whether or not this worker had any
grounds for such complaint.

5. According to OSHA standards, calculate the allowable time
for 102 dB and 120 dB exposures.

6. What is the maximum allowable dB level for an exposure of
40 minutes?

7. A worker was determined to have had violated his exposure
to noise by 12%.  Determine the noise level he was exposed
to in an 8 hour shift.

8. Determine the geometric mean of the frequency range for the
octave bands 4 through 7.

9. Determine the value of Y in: 45.5268 = 5.26Y.```
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PHYSICAL AGENTS
OSH 425, HOMEWORK SET #2

1. An 8 ft. concrete wall is constructed between a 112 dB noise
source and a worker.  The angle at which the sound waves are
reflected back at the worker is 30°.
The speed of sound in air is 331 m/sec. or 1086 ft/sec.
a) Determine the effectiveness of this wall.
b) Calculate the maximum allowable time for this worker to
attend the modified source and not to exceed the acceptable
dose of 100%.

2. Determine the constant (R) for a 12 by 12 by 10 ft. room that
is lined with 4" fiber glass material.  The ceiling and the
floor are not covered.  STATE YOUR ASSUMPTIONS IF ANY.

3. A noise source with a power level of 100 dB is installed in the
corner of a room that has a constant of 45 ft2.  Determine the
exposure level in (dB) for a worker who is 4 ft. away from this
source & attending it for 8 hours/day.

4. In a room that has a total surface area of 10000 ft2. and an
absorption coefficient of 0.2; the critical distance is
3.162 ft.  Determine the number of sources contributing to the
noise in the room forcing this given to be true.```
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PHYSICAL AGENTS
OSH 425, HOMEWORK SET #3

1. The average power of a 6 ft. diameter antenna, operating at a
frequency of 150 MHz, is 4000 watts.
a) Find its wave length.
b) Find its power density at 10 meters from the source.
STATE YOUR REASONS FOR USING THIS EQUATION.

2. Based on the ACGIH TLVs, determine the exposure limit for an
industrial microwave source operating at 25 MHz.
Also calculate its:
- Electric Field Strength.
- Magnetic Field Strength.

3. Given the magnetic field strength (H2) of 0.027 A2/m2 for a
microwave source, determine its frequency and power density.

4. An antenna is located at 30.24 meters from the beginning of its
"far field" region.  Calculate the frequency of its waves if the
diameter of this antenna is 5 ft.

5. Determine the distance between a radar and the end of its
"near field" region, if the diameter of its oval antenna is
118 inches and emitting at a frequency of 1E12 Hz.

6. The power density of an R.F./microwave source is measured to be
100 mw/cm2.  Determine or calculate its electric field and its
magnetic field strength.  WATCH FOR UNITS.```
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PHYSICAL AGENTS
OSH 425, HOMEWORK SET #4

1. The average power output of a 6.562 ft. diameter antenna is
5000 watts.  The waves are emitted at a frequency of 10 GHz.
A 2.00 meter thick wall was constructed around this antenna at
exactly 52.36 meters from the base of the antenna.
a. Determine this wall's effectiveness.
b. Find the power density (W) at 40 meters from the source.
c. Find the power density (W) at 100 meters from the source,
assuming that the wall does not exist.

Note: - STATE YOUR ASSUMPTIONS IF ANY
- WORK PROBLEMS WITH AT LEAST 4 DECIMAL PLACES

2. An antenna is located at 50 meters from the beginning of its
"far field" region.  Calculate the frequency of its waves if
if the diameter of this antenna is 8 ft.  Present your answer
in cycles/second and Hz.```
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PHYSICAL AGENTS
OSH 425, HOMEWORK SET #5

1. A radar has the following characteristics:
frequency = 20 GHz
peak power = 3.5 Mw
PRF = 250 pulses/sec
pulse width = 10 microseconds
beam width = 5 degrees
rotational frequency = 6 rpm
antenna dish diameter = 6.56 ft

Calculate:
a) wave length.
b) duty cycle.
c) average power.
d) distance to the "far field" region.
e) power density at 18 meters.
f) Using power density principles, compare exposure at
148 meters, with OSHA standards.```
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PHYSICAL AGENTS
OSH 425, HOMEWORK SET #6

1. Assuming an atmospheric attenuation of zero, calculate the
power density of a laser beam at 150 meters having the
following characteristics:
- E = 30 milliwatts
- Exit diameter (a) = 4.5 cm
- Beam divergence (q) = 0.2 milliradians.

2. Solve above problem without the stated assumption.

3. Assuming a wave length for the above beam = 315 nm and a
viewing time of 4 minutes/day, determine whether or not the
TLV is exceeded.

4. At 2 ft. from a free field radiation source the intensity
was measured to be 150 mw/cm2.  Determine the intensity at
10 and 25 ft. from this source.

5. Given the wave length of 25 cm, determine the energy range for
that wave both in eV and joules.

6. Calculate the attenuation factor for a material believed to be
a good shield against microwaves if the power density ratio of
incident to passing is 8.

7. At 15 ft. from a free field radiation source the intensity was
measured to be 300 mw/cm2.  Determine the intensity at 10 and
25 ft. from this source.```
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PHYSICAL AGENTS
OSH 425, HOMEWORK SET #7

1. At 2.00 pm. the activity of an isotope was measured to be
200 mCi.  Determine its activity at 10.00 am. of that day, given
that this isotope's half-life is 1 hour.

2. A point source produces an exposure dose rate of 5 R/hour at a
a distance of 6.00 ft.  At a distance of how many cm the dose
rate would be 400 R/hour?

3. If a gamma ray having a linear attenuation coefficient of
0.02/cm in aluminum passes through a 1.5 cm thick aluminum
plate.  What fraction will be trapped by this shield?

4. If a gamma ray having a linear attenuation coefficient of
0.8/cm in lead and the fraction trapped is 75% of its incidence,
calculate the thickness of the lead shield in inches.

5. At 2.00 pm the activity of a radioactive isotope was measured
to be 200 mCi.  Determine its activity 10 hours later, if this
isotope's half-life is 2 hours.```
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PHYSICAL AGENTS
OSH 425, HOMEWORK SET #8

1. The pressure in a car tire was 28 lb/in2 at sea level & 0 °C.
If the car was then driven for one hour and the pressure
increased to 35 lb/in2, calculate the temperature of the air
in the tire under these new conditions.

2. Prove that for every 34 ft. or 10.33 meters of diving under
water the pressure increases by 29.92" of mercury.

3. Calculate the vapor pressure for 2 gases (A) & (B) which are
occupying an enclosure that is partially filled with water
given:
- 25 grams of (gas A) at a pressure of 100 mm Hg,
MW. of (A) = 35 gm/mole.
- 125 grams of (gas B) at a pressure of 0.0724 atm,
MW. of (B) = 45 gm/mole.
Also determine the total pressure in the system.

4. Plotting the pressure in atmospheres vs. the concentration in
moles for gas (G), the regressed data indicated a slope and a
Y-intercept of 4.0821 and 0 respectively.  Determine Henry's
constant for gas (G) in atm/mole.  DO NOT MAKE ANY ASSUMPTIONS.```
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PHYSICAL AGENTS
OSH 425, HOMEWORK SET #9

1. For a 180 lb. black man wearing green/gray clothes, determine
the WBGT for both indoors and outdoors given the following
conditions:
- Air temperature = 82 °F
- Globe temperature = 96 °F
- Wet-bulb temperature = 68 °F

2. At the following environmental conditions:
- Air temperature = 85 °F
- Globe temperature = 95 °F
- Wet-bulb temperature = 75 °F
- Vpa = 22.5 mm Hg (from the psychrometric chart)
- velocity of air = 500 ft/minute.
a) Determine the HSI for a 180 lb. man wearing white clothes
& shoveling concrete at a rate assumed to be a heavy load.
His metabolic heat gain is approximately 1800 BTU/hr.
b) Calculate his work/rest cycle.
NOTE: SOLVE THIS PART BY THE 2 DIFFERENT METHODS WE COVERED.```
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