Nokea
What unit is used for measuring luminous flux, which indicates the perceived brightness of a light source by the human eye?
- A. Candela
- B. Lumen
- C. Lux
- D. Hertz
Correct Answer: B
Rationale: Lumen is the correct unit for measuring luminous flux, which quantifies the total visible light emitted by a source per unit of time. Candela measures luminous intensity, lux measures illuminance, and Hertz measures frequency. Therefore, in the context of measuring the perceived brightness of a light source by the human eye, luminous flux is quantified in lumens.
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Which indicator is commonly used to distinguish between acidic and basic solutions?
- A. Methyl orange
- B. Phenolphthalein
- C. Universal indicator
- D. All of the above are common indicators.
Correct Answer: B
Rationale: Phenolphthalein is commonly used to differentiate between acidic and basic solutions. It changes color, turning pink in basic solutions and remaining colorless in acidic solutions due to a specific pH range. While methyl orange and universal indicator are also indicators used for pH testing, phenolphthalein is especially known for its distinctive color change in response to acidic and basic solutions, making it the correct choice. Methyl orange is typically used in titrations for a sharp color change at a specific pH, and the universal indicator is a mixture of indicators displaying a range of colors depending on the pH value, not specifically tailored to acidic and basic distinctions.
Which process involves the body's natural defense against inhaled dust and allergens?
- A. Cellular respiration
- B. Gas exchange
- C. Ciliary action
- D. Bronchoconstriction
Correct Answer: C
Rationale: Ciliary action refers to the process where tiny hair-like structures called cilia in the respiratory tract help to sweep away inhaled dust and allergens, preventing them from entering deeper into the lungs. This is a crucial part of the body's natural defense mechanism against respiratory irritants. Cellular respiration (A) is the process where cells use oxygen to produce energy, not a defense mechanism against inhaled particles. Gas exchange (B) involves the exchange of oxygen and carbon dioxide in the lungs, not specifically targeting inhaled dust and allergens. Bronchoconstriction (D) is the narrowing of the airways in response to irritants or allergens, which can lead to breathing difficulties, but it is not the primary defense mechanism against these particles.
What element is responsible for the red color of blood?
- A. Magnesium
- B. Iron
- C. Copper
- D. Zinc
Correct Answer: B
Rationale: The correct answer is B: Iron. Hemoglobin, the protein responsible for carrying oxygen in red blood cells, contains iron in its heme group, contributing to the blood's characteristic red color. Magnesium (choice A), copper (choice C), and zinc (choice D) are not responsible for the red color of blood. Magnesium is an essential mineral involved in various physiological processes, copper is a trace element important for enzyme function, and zinc is a micronutrient essential for multiple cellular functions but not related to the red color of blood.
Which fibrous connective tissue connects a muscle to a bone, allowing movement at a joint?
- A. Tendon
- B. Ligament
- C. Cartilage
- D. Bursa
Correct Answer: A
Rationale: Tendons, the correct answer, are fibrous connective tissues that connect muscles to bones, enabling movement at joints. They play a crucial role in transmitting the force generated by muscles to the bones, facilitating movement. Ligaments (option B) connect bone to bone, providing stability to joints. Cartilage (option C) is a flexible tissue that acts as a cushion, reducing friction between bones in joints. Bursae (option D) are fluid-filled sacs located near joints that help reduce friction between tissues such as tendons and bones.
What happens to the density of a gas when its temperature increases at constant pressure?
- A. It increases.
- B. It decreases.
- C. It remains the same.
- D. Information is insufficient.
Correct Answer: B
Rationale: When the temperature of a gas increases at constant pressure, the average kinetic energy of the gas molecules increases. This leads to the gas molecules moving faster and spreading out more, which causes them to occupy a larger volume. As a result, the density of the gas decreases because the same number of gas molecules are now distributed over a larger space. Choice A is incorrect because as the gas molecules spread out, the density decreases. Choice C is incorrect because the increase in temperature leads to a decrease in density due to the increased volume occupied by the gas molecules. Choice D is incorrect because with the provided scenario of temperature increase at constant pressure, the effect on density can be determined.