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Comments (10)
Tam Li June said
at 6:27 pm on Jan 25, 2014
Hi Mr Ang, could you explain example 10.2 of the general waves notes once again for the p case and also for the one where the particle is at the crest or trough ? May I check why will the velocity be 0 at the crest or trough?
Thank you for your help.
johnlittlephysics said
at 10:54 am on Feb 3, 2014
View the first two videos above and post further questions here.
johnlittlephysics said
at 11:06 am on Feb 3, 2014
When a particle is reaching the crest or trough position, it decelerates to a stop (v = 0) before accelerating in the opposite direction. Just like a ball thrown upwards, it is instantaneously at rest at the highest point.
myuemin63@gmail.com said
at 7:05 pm on Feb 17, 2014
Mr. Ang, for drawing of both reflected and refracted plane wavefronts, is there any minimum number of wavefronts that we have to draw for each question?
johnlittlephysics said
at 7:50 pm on Feb 17, 2014
Normally, draw as many within the space provided, say at least 5.
Guo Lilian said
at 12:20 pm on Sep 22, 2014
Hi Mr Ang,
When does reflection and refraction occur (for light waves, sound waves, and water waves)? Can they occur simultaneously?
johnlittlephysics said
at 1:37 pm on Sep 22, 2014
If you refer to the Waves mindmap at http://phyglossary.pbworks.com/w/page/85358083/m
you would see that reflection and refraction are properties of waves in general, although you encounter it specifically for light and water waves.
In general all mechanical and electromagnetic waves may undergo reflection or refraction or both, under suitable conditions.
For light rays reaching a boundary, if refraction occurs, partial reflection would also occur.
Guo Lilian said
at 2:57 pm on Sep 22, 2014
Are water and sound waves also partially reflected when refraction occurs? When a sound wave produces an echo after reflecting off a surface, has it also been propagated through the medium?
johnlittlephysics said
at 3:09 pm on Sep 22, 2014
1. Possibly, but we have not done these in our content syllabus.
There is also some energy loss by absorption by the 2nd medium in general.
2. If the surface is flat , smooth and hard, the echo is mainly sound from reflection. A little sound energy is absorbed, and a little may be transferred via refraction.
Guo Lilian said
at 3:14 pm on Sep 22, 2014
Okay, thank you :)
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