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Positron emission tomography (PET) scans utilize a key property of positrons for medical imaging. What is this property?
- A. High mass
- B. Positive charge
- C. Extreme stability
- D. Identical behavior to electrons
Correct Answer: B
Rationale: Positron emission tomography (PET) scans utilize the property of positrons having a positive charge. Positrons are the antimatter counterpart of electrons, having the same mass but opposite charge. When a positron collides with an electron, they annihilate each other, producing gamma rays that can be detected by the PET scanner to create images of the body's internal structures and functions. Choice A is incorrect because positrons have the same mass as electrons. Choice C is incorrect as positrons are not extremely stable due to their tendency to annihilate when they encounter electrons. Choice D is incorrect as positrons exhibit different behavior than electrons due to their opposite charges.
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What happens to the concentration of hydrogen ions (\([H^+]\)) in a solution as the pH increases?
- A. Increases
- B. Decreases
- C. Remains constant
- D. Becomes neutral
Correct Answer: B
Rationale: As the pH increases, the concentration of hydrogen ions decreases. The relationship is inversely proportional
What phenomenon occurs when a wave encounters a change in medium causing a change in its speed and direction?
- A. Refraction
- B. Reflection
- C. Diffraction
- D. Interference
Correct Answer: A
Rationale: Refraction is the phenomenon that occurs when a wave encounters a change in medium, causing a change in its speed and direction. This change in speed and direction is due to the wave bending as it passes from one medium to another with a different density. It is essential to understand refraction as it plays a crucial role in various phenomena, such as the bending of light in lenses, the formation of rainbows, and the way seismic waves travel through the Earth's layers. Reflection, while also a wave phenomenon, involves the bouncing back of a wave when it encounters a boundary. Diffraction refers to the bending of waves around obstacles or through openings, and interference involves the combination of two or more waves to form a new wave pattern.
What is the product of the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH)?
- A. NaCl + H2O
- B. NaOH + HCl
- C. Na2Cl + H2O
- D. NaClO3 + H2
Correct Answer: A
Rationale: When hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), it forms sodium chloride (NaCl) and water (H2O) according to the following chemical equation: HCl + NaOH -> NaCl + H2O. Therefore, the correct answer is NaCl + H2O (Choice A). This reaction is a classic acid-base neutralization reaction where the acid (HCl) reacts with the base (NaOH) to form a salt (NaCl) and water (H2O). Choice B (NaOH + HCl) is incorrect because the order of the reactants matters in a chemical reaction, and in this case, HCl is the acid reacting with NaOH. Choices C (Na2Cl + H2O) and D (NaClO3 + H2) are incorrect because they do not represent the products of the reaction between HCl and NaOH as per the balanced chemical equation.
Which of the following terms refers to a muscle that lengthens while another muscle contracts to produce movement?
- A. Synergist
- B. Agonist
- C. Antagonist
- D. Flexor
Correct Answer: C
Rationale: The correct answer is 'Antagonist.' An antagonist muscle is a muscle that lengthens while another muscle (agonist) contracts to produce movement. The antagonist muscle relaxes to allow the agonist muscle to contract effectively. In this scenario, the antagonist muscle works in opposition to the agonist muscle, providing control and precision to movement. The other choices are incorrect because a synergist muscle assists the agonist muscle in performing a movement, an agonist muscle is the primary muscle responsible for generating movement, and a flexor muscle is a muscle that decreases the angle at a joint.
Muscles that work in opposition to each other, producing opposing movements, are called:
- A. Synergists
- B. Antagonists
- C. Agonists
- D. Fixators
Correct Answer: B
Rationale: Antagonist muscles are pairs of muscles that work in opposition to each other, producing opposing movements. When one muscle contracts, the other relaxes to allow the movement to occur smoothly. Synergists are muscles that work together to create a movement, not in opposition. Agonists are muscles primarily responsible for producing a specific movement, not opposing each other. Fixators are muscles that stabilize joints to allow other movements to take place, providing a stable base for muscle actions but do not produce opposing movements.