One end of a horizontal string is fixed to a
wall. A transverse wave pulse in the form of a
crest is generated at the other end and moves
toward the wall, as shown. Consider the pulse
after it has been reflected by the wall.
v
What is/are correct concerning the re-
flected pulse?
A) The reflected pulse forms a valley.
B) The reflected pulse has a greater speed
than that of the incident pulse.
C) The reflected pulse has the same shape
as the incident pulse.
A) The reflected pulse forms a valley.
To determine if the given statements are correct or not, we need to understand how wave pulses behave when they are reflected.
When a wave pulse encounters a fixed end, such as a wall, it undergoes reflection. During reflection, the pulse changes direction and travels back through the medium in the opposite direction.
Let's analyze each statement:
A) "The reflected pulse forms a valley."
When a crest pulse is incident on the wall, it will get reflected as a trough pulse. A crest corresponds to the highest point of a wave, while a trough corresponds to the lowest point. Hence, statement A is incorrect. The correct statement would be: "The reflected pulse forms a trough."
B) "The reflected pulse has a greater speed than that of the incident pulse."
The speed of a wave pulse depends on the characteristics of the medium through which it travels, such as its density and tension. In this case, since one end of the string is fixed to the wall, the tension in the string remains the same. Therefore, the speed of the reflected pulse will be the same as the speed of the incident pulse. Therefore, statement B is incorrect. The correct statement would be: "The reflected pulse has the same speed as that of the incident pulse."
To summarize:
A) False. The reflected pulse forms a trough.
B) False. The reflected pulse has the same speed as that of the incident pulse.
The correct statement(s) concerning the reflected pulse are:
A) The reflected pulse forms a valley.
When a wave is reflected at a fixed boundary, such as a wall in this case, the reflected wave is inverted. This means that a crest in the incident pulse will be transformed into a valley in the reflected pulse.
B) The reflected pulse has a greater speed than that of the incident pulse.
The speed of a wave is determined by the medium through which it is propagating. When a wave is reflected, it generally does not change its speed. Therefore, the speed of the reflected pulse is likely to be the same as that of the incident pulse.