QUESTION 17 All electromagnetic waves travel at the speed of light which is A. 30 km/s B. 300 km/s C. 3000 km/s D. 30,000 km/s QUESTION 18 In concert halls, soft materials and carpet are used to ____ sound. A. reflect B. refract C. deflect D. absorb QUESTION 19 In order for sound waves to be transmitted over long distances within a town, they have to be converted into a/an A. microwave. B. ultraviolet ray. C. electrical current. D. electromagnetic wave. QUESTION 20 Astronauts in space use radio waves to communicate because A. there is electricity in space. B. there are no air particles in space.
Answer (1)
Let's break down each question one by one to provide clear and accurate answers.
QUESTION 17: All electromagnetic waves travel at the speed of light, which is a fundamental constant of nature. The correct choice is D. 30,000 km/s . To be more precise, the speed of light in a vacuum is approximately 299,792 kilometers per second, but it is often rounded to 300,000 km/s for simplicity in general discussions.
QUESTION 18: In concert halls, soft materials and carpets are used to manage sound. The correct answer here is D. absorb . These materials absorb sound to reduce echoes and reverberations, leading to better acoustics within the space by preventing sound waves from reflecting too much across the hall.
QUESTION 19: For sound waves to be transmitted over long distances, they are typically converted into electrical signals. Therefore, the correct answer is C. electrical current . These electrical signals can then be processed, amplified, and transmitted efficiently, often using electromagnetic waves, to cover large distances and eventually be converted back into sound.
QUESTION 20: In the vacuum of space, there are no air particles to transmit sound waves; hence, astronauts use radio waves to communicate. The correct answer is B. there are no air particles in space . Radio waves, which are a type of electromagnetic wave, do not require a medium with particles to travel through, so they can move through the vacuum of space and are ideal for communication in these environments.
