Nokea
What is the term for the phenomenon when two waves combine to form a new wave?
- A. Diffraction
- B. Interference
- C. Refraction
- D. Dispersion
Correct Answer: B
Rationale: The correct answer is B: Interference. Interference is the term used to describe the phenomenon when two waves combine to form a new wave. When waves interact constructively or destructively, they interfere with each other, resulting in a new wave pattern. Choice A, Diffraction, refers to the bending of waves around obstacles, not the combination of waves. Choice C, Refraction, is the bending of waves as they pass from one medium to another, not the combination of waves. Choice D, Dispersion, is the separation of light into its different colors, not the combination of waves.
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What is the main function of the endoplasmic reticulum (ER) in the cell?
- A. To synthesize and transport proteins and lipids
- B. To package and transport proteins
- C. To break down macromolecules
- D. To store genetic material
Correct Answer: A
Rationale: The endoplasmic reticulum (ER) is a network of membranes within the cell that plays a crucial role in protein and lipid synthesis. It consists of two types: rough ER, which is studded with ribosomes and involved in protein synthesis, and smooth ER, which is involved in lipid synthesis and detoxification. The ER's main function is to synthesize proteins and lipids, not just package and transport them. While the ER is involved in transporting these synthesized proteins and lipids to other parts of the cell or outside the cell, its primary role is in their synthesis. Breaking down macromolecules is primarily the function of lysosomes, which are membrane-bound organelles containing enzymes for digestion. Storing genetic material is the function of the nucleus, which houses the cell's DNA. The ER is not involved in storing genetic material.
What is the technical term for the involuntary muscular contractions that move food through the digestive tract?
- A. Segmentation
- B. Peristalsis
- C. Chylification
- D. Emulsification
Correct Answer: B
Rationale: Peristalsis is the term used to describe the involuntary muscular contractions that move food through the digestive tract. This process involves rhythmic contractions and relaxations of the muscles in the digestive system, which help propel food from the esophagus to the stomach and through the intestines for digestion and absorption of nutrients. Segmentation refers to the mixing movements in the intestines that aid in the absorption of nutrients but is not the term for the movement of food through the digestive tract. Chylification is not a recognized term in digestive physiology. Emulsification is the process of breaking down fat globules into smaller droplets to aid in digestion, not the movement of food through the digestive tract.
The critical angle is defined as the minimum angle of incidence in a denser medium for which light undergoes:
- A. Total internal reflection
- B. Continued refraction
- C. Specular reflection
- D. Increased dispersion
Correct Answer: A
Rationale: The critical angle is the minimum angle of incidence in a denser medium at which light undergoes total internal reflection instead of refraction. This phenomenon occurs when light travels from a denser medium to a less dense medium, and the angle of incidence is greater than the critical angle. Total internal reflection is a crucial concept in optics and is utilized in various applications such as fiber optics and prisms. Choice B, 'Continued refraction,' is incorrect as the critical angle specifically marks the point at which total internal reflection occurs, not continued refraction. Choice C, 'Specular reflection,' does not accurately describe the phenomenon associated with the critical angle. Choice D, 'Increased dispersion,' is unrelated to the concept of the critical angle and does not describe the behavior of light at this specific point.
How do vaccines work?
- A. By directly killing pathogens
- B. By introducing weakened or inactive versions of pathogens to trigger an immune response
- C. By stimulating the immediate production of specific antibodies
- D. None of the above
Correct Answer: B
Rationale: Vaccines work by introducing weakened or inactive versions of pathogens to trigger an immune response in the body. This exposure helps the immune system recognize and remember the pathogen, enabling a faster and more effective response upon future exposure. Vaccines do not directly kill pathogens but prepare the immune system for a potential encounter, enhancing protection. They also do not stimulate the immediate production of specific antibodies as the immune response takes time to develop upon vaccination. Choice A is incorrect because vaccines do not kill pathogens directly; they prime the immune system to recognize and respond to them. Choice C is incorrect because while vaccines lead to the production of specific antibodies, it is not immediate, as it takes time for the immune response to develop and produce these antibodies.
Which radioactive isotope is commonly used in medical imaging techniques such as PET scans?
- A. Uranium-235
- B. Plutonium-239
- C. Potassium-40
- D. Fluorine-18
Correct Answer: D
Rationale: Fluorine-18 is the radioactive isotope commonly used in medical imaging techniques such as PET scans. It is frequently used in the form of fluorodeoxyglucose (FDG) to locate areas of heightened metabolic activity in the body, such as in cancer cells. Uranium-235 and Plutonium-239 are not typically employed in medical imaging, and Potassium-40, while a naturally occurring radioactive isotope found in the human body, is not commonly used in medical imaging techniques.