1. In a standing wave, the medium at the tip of a loop is
a) showing destructive interference
b) not moving
c) at the original amplitude of the wave
d) showing constructive interference
my answer: b
2. If a motorcycle is travelling toward an observer the frequency the observer hears is ___ the actual sound made by the motorcycle
a) greater than
b) lower than
c) smaller than
d) the same as
my answer: a
To answer these questions, let's break down the concepts and process for finding the correct answers:
Question 1:
The question is asking about the medium at the tip of a loop in a standing wave. To understand this, we need to know what standing waves are and how they work.
A standing wave is formed when two waves of the same frequency, amplitude, and wavelength traveling in opposite directions interfere with each other. This interference creates points in the wave where the displacement of the medium is always zero. These points are called nodes.
In a standing wave, the medium at the tip of a loop is always at the original amplitude of the wave. It doesn't experience complete destructive or constructive interference. Hence, the correct answer is (c) at the original amplitude of the wave.
Question 2:
This question is related to the phenomenon of the Doppler effect. To determine the answer, we need to understand how the frequency of sound changes when a source is traveling towards or away from an observer.
The Doppler effect states that when a source of sound is moving towards an observer, the frequency heard by the observer is higher (greater) than the actual frequency of the sound made by the source. Similarly, when the source is moving away from the observer, the frequency heard by the observer is lower.
In this case, the motorcycle is traveling towards the observer. Therefore, the frequency the observer hears is greater than the actual sound made by the motorcycle. So, the correct answer is (a) greater than.
Remember, understanding the concepts behind the questions is essential to arrive at the correct answers.