Questions 41-43 concern the reflection of sound, uses of radioactivity, and convex lenses. Provide the answers to these questions.

Here are the answers to the questions: Question 41: Step 1: Analyze Figure 7. Figure 7 shows sound waves being produced and then reflecting off a large reflecting wall. The students are likely measuring the time taken for the sound to travel to the wall and back, which is used to determine the speed of sound. Step 2: Identify the physical phenomenon. When sound waves bounce off a surface, the phenomenon is called reflection. The correct option is C. C) Reflection Question 42: Step 1: Evaluate each statement regarding the uses of radioactivity. A. Radioactivity is used in determining the thickness of films (e.g., using beta radiation to monitor paper thickness). This is a valid use. B. Refrigerators operate based on thermodynamic principles (refrigerant cycles, compression, expansion) and do not use radioactivity in their primary action. C. Radioactive tracers are widely used in medicine (e.g., PET scans) and industry to track substances. This is a valid use. D. Gamma radiation is used for sterilizing medical equipment and food products. This is a valid use. Step 2: Identify the exception. The action of a refrigerator does not involve radioactivity. The correct option is B. B) It is used in the action of a refrigerator Question 43: Step 1: Analyze Figure 2 (referred to as Figure 7 in the question). Figure 2 shows a convex lens forming an image of a candle. The object (candle) is at 30 cm, and the image is formed at 45 cm. The image is real (formed on a screen), inverted, and larger than the object (magnified). Step 2: Determine which optical instrument produces a real, inverted, and magnified image. A. A projector uses a convex lens to produce a real, inverted, and magnified image of a slide or film onto a screen. B. A magnifying glass produces a virtual, upright, and magnified image. C. A simple camera produces a real, inverted, and diminished image. D. A photocopier typically produces an image of the same size or slightly reduced/enlarged. The correct option is A. A) Projector Question 44: Step 1: Analyze the image characteristics from Figure 2. The image formed is larger than the object (magnified). For a convex lens, a real, inverted, and magnified image is formed when the object is placed between the focal point (F) and twice the focal length (2F). In this case, the image is formed beyond 2F on the other side of the lens. Step 2: Relate image size to image position. Since the image is magnified, the object must be between F and 2F. Consequently, the image is formed beyond 2F. The correct option is A. A) Beyond 2F Question 45: Step 1: Identify the object distance (u) and image distance (v) from Figure 2. Object distance, u = 30 cm. Image distance, v = 45 cm. Since the image is real, v is positive. Step 2: Use the lens formula to calculate the focal length (f). The lens formula is: (1)/(f) = (1)/(u) + (1)/(v) Substitute the values: (1)/(f) = (1)/(30 cm) + (1)/(45 cm) Find a common denominator, which is 90: (1)/(f) = (3)/(90 cm) + (2)/(90 cm) (1)/(f) = (5)/(90 cm) (1)/(f) = (1)/(18 cm) f = 18 cm Step 3: Compare the calculated focal length with the given options. The focal length is 18 cm. A. 30 cm B. Greater than 30 cm C. 60 cm D. Less than 30 cm 18 cm is less than 30 cm. The correct option is D. D) Less than 30 cm Question 46: Step 1: Identify the object distance (u) and image distance (v) from Figure 2. Object distance, u = 30 cm. Image distance, v = 45 cm. Step 2: Calculate the magnification (M). Magnification is given by: M = (v)/(u) Substitute the values: M = 45 cm30 cm M = 1.5 The correct option is C. C) 1.5 Question 47: Step 1: Analyze Figure 8. Figure 8 shows a spring with a mass attached, causing it to extend. The original length and the extended length are shown. This setup demonstrates how a spring stretches under an applied force. Step 2: Identify the physical law related to spring extension and force. Hooke's law states that the force required to extend or compress a spring is directly proportional to the distance of extension or compression, within its elastic limit (F = ke). The correct option is D. D) Hooke's law Question 48: Step 1: Consider the function of a spring in this experiment. For the experiment to work correctly, the spring must stretch when a force is applied and return to its original length when the force is removed. Step 2: Identify the material property that