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52 Cards in this Set
- Front
- Back
What is refraction?
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The bending of light as light goes from one medium to another, due to change in speed of light in different media.
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The bending of light as light goes from one medium to another is called ____________
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Refraction.
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Why does an object look "bent" when placed in water?
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Refraction, the bending of light as light goes from one medium to another, due to change in speed of light in different media.
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Do objects in water appear closer than they really are, or farther away than they really are? By how much?
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Closer, due to refraction. Objects appear 25% closer.
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How much closer do objects appear underwater?
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25%
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What is the magnification of objects underwater?
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4/3, or 33%. So if you think you see a 4m long shark, it's really 3m long.
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Do objects look 25% closer underwater or 33% closer underwater?
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25% closer, 33% larger.
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What is visual reversal?
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When objects are in cloudy water, they are obscured, which the eye associates with being further away than they really are.
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Do objects in cloudy water look further away or closer than they really are? Why?
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Further away due to visual reversal.
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What is gauge pressure?
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The pressure of the water without the atmosphere. 33' = 1 atmosphere gauge.
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What is absolute pressure?
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Gauge pressure + 1 atmosphere. (If at sea level. Less at altitude). 33' = 2 atmospheres absolute = 2 ATA.
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What is the abbreviation ATA?
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ATmospheres Absolute.
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What is ambient pressure?
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Surrounding pressure = absolute pressure.
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Two of these are the same. Which ones? Ambient Pressure; Gauge Pressure; Absolute Pressure.
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Ambient = Absolute.
Gauge = Absolute - 1 atmosphere. |
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What is Dalton's Law?
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In a mixture of gases, each gas exerts its individual pressure independent of other gases in the mixture (partial pressure).
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Which law asserts that pressures of mixed gasses are independent?
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Dalton's Law.
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What is surface equivalency?
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The fraction of a gas you would have to breathe at the surface to produce the same effect at a particular gas, e.g., if air has 0.5% CO, breathing it at 132 feet would be the equivalent of breathing a 2.5% CO mix.
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What is Henry's Law?
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If pressure decreases on a liquid, dissolved gases come out of solution.
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Which law dictates that if pressure decreases on a liquid, gas comes out of solution?
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Henry's Law.
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What is Boyle's Law?
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Pressure is inversely related to volume.
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Which law says that at 33' the pressure is 2 ATA?
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Boyle's Law.
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What is gas tension?
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The pressure exerted by gasses dissolved in a liquid. The more gas that is dissolved in a liquid, the greater the gas tension.
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What is supersaturation?
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When gas is dissolved in a liquid at equilibrium, then surface pressure is reduced, gas tension becomes higher than the surface tension, and the gas comes out of solution.
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What is conduction?
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Transmission of heat by direct contact.
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What is transmission of heat by direct contact called?
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Conduction.
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What is convection?
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Transmission of heat by fluids.
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What is transmission of heat by fluids called?
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Convection.
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What is radiation?
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Transmission of heat by electromagnetic waves.
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What is the transmission of heat by electromagnetic waves called?
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Radiation.
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What are the three ways heat is transmitted?
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Radiation, convection, and conduction.
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Which of the three ways heat is transmitted is most important to diving?
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Conduction.
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Water conducts heat how many times faster than in air?
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20 times.
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Which does water conduct 20 times faster, sound or heat?
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Heat.
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How much larger does refraction make objects look underwater?
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33%, or a ratio of 4:3.
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Water conducts sound how many times faster than in air?
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4 times.
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Which does water conduct 4 times faster, sound or heat?
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Sound.
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What does a cubic foot of seawater weigh?
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64 pounds.
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Which weighs 64 pounds, a cubic foot of seawater or fresh water?
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Seawater.
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What does a cubic foot of fresh water weigh?
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62.4 pounds.
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Which weighs 62.4 pounds, a cubic foot of seawater or fresh water?
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Fresh water.
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How many feet of seawater adds one atmosphere of pressure?
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33.
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How many feet of fresh water adds one atmosphere of pressure?
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34.
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Diving 33 feet adds one atmosphere of pressure in which, seawater or fresh water?
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Seawater.
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How do you convert Fahrenheit to Rankine?
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Fahrenheit + 460
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What is the temperature scale that starts from absolute zero but uses degrees the same size as Fahrenheit?
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Rankine.
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Buoyancy = Weight of Object - Weight of ___________.
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Displaced water of the object.
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How much does pressure change for every degree Fahrenheit?
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5 PSI for every 1 degree F.
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If a tank starts at 3000 psi at 70F, and the tank is chilled in the water to 55F, what will the pressure be?
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2925 PSI - 5 PSI for every degree, and (70 - 55) = 15, 15 x 5 = 75 PSI difference. 3000 - 75 = 2925 PSI.
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What is the pressure, volume, temperature formula?
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(P1 x V1) / T1 = (P2 x V2) / T2.
Remember to convert F to Rankine (F + 460). |
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Why is water able to conduct hear more efficiently than air?
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Water is more dense than air.
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What is the relationship between PSI and ATA?
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14.7 PSI = 1 ATA.
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If a tank is filled to 3000 PSI, how many atmospheres of gas is that?
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~200 ATA.
3000 PSI / (14.7 PSI / 1 ATA) = 200. |