“Reflection of Waves” MHT-CET Class 12 Physics Crash Course | Chapter – Superposition of Waves
In this session G.S. Khairnar discussed the theory and MCQ’s of “Reflection of Waves”. The session will be useful for all the aspirants of MHT-CET 2022. The session will be in Marathi and English.
Reflection of Waves:-
Hello dear students we have learnt about the reflection of light in details in std 9th and std 10th. During reflection of light from materials like plane mirror, lateral deviation is produced, and after reflection the rays of light remains in the same medium from which it gets incident with some changes in energy, intensity etc. In this article we are going to discuss about the reflection of waves i.e. longitudinal wave and transverse wave. Before that, let’s just recall about these waves through the following distinguishing characteristics.
Reflection of waves:
When beam is incident on a concave mirror a beam are reflected in such a way that they converge at a single point. On the other hand, when the parallel beam is reflected from the surface of a convex mirror, all the rays move away from each other, giving rise to a diverging beam of light.
Let’s learn the reflection of transverse waves…!
When a crest or a trough of transverse waves incident normally on denser medium, the wave gets reflected due to change in medium. The particles of crest move in upward direction and get reflected as trough moves vertically downward direction because the wave velocity gets reversed. Hence there is change of phase by 1800. Therefore the crest is reflected as trough and trough is reflected as crest.
Similarly during reflection of transverse wave from the rarer medium, crest reflected as crest and trough reflected as trough.
Reflection of longitudinal waves…!
When a compression or rarefaction of a longitudinal wave is incident normally on a denser medium like rigid wall. The particle of the medium (i.e. wall) are perfectly rigid and stationary, the wave gets reflected due to change in medium. So by Newton’s 3rd law of motion same pressure is exerted by wall. Thus compression is reflected back as compression and rarefaction is reflected back as rarefaction.
But if the medium is rarer then compression is reflected as rarefaction and rarefaction is reflected as compression.
Reflection of Waves:-
Let’s solve some MCQ’s…..!
Q.1) Transverse wave can propagate in…
a) solids only
b) liquids only
c) gases only
d) all of above
Answer
a) solids only
Q.2) Longitudinal wave can propagate in…
a) solids only
b) liquids only
c) gases only
d) all of above
Answer
d) all of above
Q.3) For propagation of transverse wave material should possess the elasticity of……
a) shape
b) volume
c) both shape and volume
d) none of these
Answer
a) shape
Q.4) When transverse wave strikes the denser material it gets reflected such that……
a) crest becomes crest
b) trough becomes trough
c) crest becomes trough and trough becomes crest
d) can not predicted
Answer
c) crest becomes trough and trough becomes crest
Q.5) During reflection of longitudinal wave from the denser medium, compression is reflected as…
a) rarefaction
b) compression
c) either ‘a’ or ‘b’
d) can not predicted
Answer
b) compression
Q.6) During reflection of longitudinal wave from the rarer medium, compression is reflected as…
a) rarefaction
b) compression
c) either ‘a’ or ‘b’
d) can not predicted
Answer
a) rarefaction
Q.7) When transverse wave and longitudinal wave is reflected from the surface of denser medium, the phase of wave changes by…
a) 00
b) 900
c) 1800
d) 3600
Answer
c) 1800
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