Tidal Volume represents the normal volume of air displaced in the lungs with inhalation and exhalation without any additional effort. Any air in the upper respiratory tract not involved in the exchange is referred to as Dead Air.
This is increased with the use of a snorkel and regulator which is why it's so important to breathe in a full, relaxed manner to ensure exhaled air has cleared the increased dead air space.
The phenomenon of light bending obliquely as it passes through mediums of different densities is called refraction. This can be observed when viewing an object through a glass of water.
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The answer for this can be found in the PADI Instructor Manual - Divemaster Course - Section 4 and in the student materials for the PADI Divemaster program.
The three knots give a basic introduction to line use on water vessels and underwater and also give them an insight into the PADI Search and Recovery Specialty Diver course.
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The answer to this can be found in your PADI Instructor Manual in the Paperwork and Admin Procedures section under the heading Knowledge Development Assesment.
Each incorrect answer should be reviewed after completion of any Knowledge Development, Quiz, Quick Review and Exam and retesting should happen for those scoring less than 75%.
If a cylinder is filled to a greater pressure then the test specifications and non-reclosing rupture disk located in the valve assembly.
This allows excess pressure to vent from the cylinder valve and thus avoids the rupture of the cylinder body itself.