What is the difference between a real image and a virtual image formed by a lens?
- A. Real images can be projected onto a screen, while virtual images cannot.
- B. Real images are always upright, while virtual images can be inverted.
- C. Real images are formed by converging lenses, while virtual images are formed by diverging lenses.
- D. All of the above are true.
Correct Answer: A
Rationale: The correct answer is A. Real images can be projected onto a screen because they are formed by the actual convergence of light rays, while virtual images cannot be projected onto a screen as they appear to diverge from a point behind the lens. Real and virtual images do not have a consistent orientation (upright or inverted), so option B is incorrect. Real images are formed by both converging and diverging lenses depending on the specific scenario, so option C is not a definitive distinction. Option D is incorrect as not all the statements are true. Therefore, the only accurate general distinction between real and virtual images is that real images can be projected onto a screen, while virtual images cannot.
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What is the term for the number of moles of solute per liter of solution?
- A. Molarity
- B. Molality
- C. Normality
- D. Concentration
Correct Answer: A
Rationale: Molarity is the correct term for the number of moles of solute per liter of solution. It is expressed as moles of solute divided by liters of solution. Molality (B) is similar but is moles of solute per kilogram of solvent. Normality (C) is the number of equivalents of solute per liter of solution, and Concentration (D) is a general term for the amount of solute present in a given quantity of solution. Therefore, the correct answer is A, molarity, as it specifically refers to moles of solute per liter of solution.
Which of the following is NOT a property of a catalyst?
- A. Increases the rate of a reaction
- B. Remains unchanged after the reaction
- C. Lowers the activation energy
- D. Creates new products
Correct Answer: D
Rationale: A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It remains unchanged after the reaction, which eliminates option B. A catalyst works by lowering the activation energy required for the reaction to occur, which eliminates option C. A catalyst does not create new products in a reaction; it only facilitates the conversion of reactants into products more efficiently. Therefore, option D is NOT a property of a catalyst.
What is the principle behind the phenomenon of refraction, where waves bend when entering a new medium?
- A. Change in wavelength
- B. Change in frequency
- C. Change in wave speed
- D. None of the above
Correct Answer: C
Rationale: Refraction occurs due to a change in wave speed when waves enter a new medium. As waves travel from one medium to another, their speed changes, causing them to bend. This change in speed is responsible for the bending of waves during refraction. It is not the change in wavelength or frequency that causes refraction, but rather the change in speed as waves move through different mediums. Therefore, the correct answer is the change in wave speed (Choice C). Choices A and B are incorrect as refraction is not primarily influenced by changes in wavelength or frequency, but by changes in wave speed. Choice D is also incorrect as there is a specific principle, which is the change in wave speed, behind the phenomenon of refraction.
Which hormone, produced by the pancreas, is released in response to low blood sugar levels and stimulates the release of glucose into the bloodstream?
- A. Insulin
- B. Glucagon
- C. Cortisol
- D. Thyroxine
Correct Answer: B
Rationale: Glucagon is the hormone produced by the pancreas that is released in response to low blood sugar levels. It acts to stimulate the release of glucose into the bloodstream by promoting the breakdown of glycogen in the liver. Insulin, conversely, is released in response to high blood sugar levels and promotes the uptake of glucose by cells. Cortisol is a steroid hormone produced by the adrenal glands that regulates metabolism and the immune response. Thyroxine is a hormone produced by the thyroid gland that regulates metabolism but is not involved in responding to low blood sugar levels.
Identify the element with the electron configuration: 1s2 2s2 2p6 3s2 3p6. To which group and period does this element belong?
- A. Group 16, Period 3
- B. Group 14, Period 3
- C. Group 18, Period 3
- D. Group 17, Period 2
Correct Answer: C
Rationale: The given electron configuration matches that of Argon, an element found in Group 18 of the periodic table. This element is in the third period, as indicated by the highest energy level (n=3) where electrons are present. Therefore, the correct answer is Group 18, Period 3. Choice A (Group 16, Period 3) corresponds to sulfur, not the given electron configuration. Choice B (Group 14, Period 3) corresponds to silicon, not the given electron configuration. Choice D (Group 17, Period 2) corresponds to chlorine, which is in Period 3 but not in Group 18, making it incorrect for the given electron configuration.