Some help on light

[Sigmarus]

So i have a homework question regarding the topic "light".Here's the question(Note:This is a three part question and i am only asking the 3rd part,the whole question basically asked me to plot the graph of angle of incidence and refraction when a light ray is shined through air and then liquid(transparent),and predict the angle of refraction with a given number of angle of incidence.)

Martin had,on several occasions,accidentally pushed the container containing the liquid medium.As a result,some light was observed to have reflected iff the boundary of the liquid medium instead of passing through it.Martin saw a blur image of himself on the disturbed liquid medium.

Suggest why the disturbance of the liquid medium could result in the formation of a blur and unclear reflected image of Martin.

Any basic but vivid explaination would be greatly appreciated(Since i'm only learning pretty much the basics of light)

 

Thanks

[swansont]

What can you say about a disturbed liquid that's different from an undisturbed one, or a solid?

[studiot]

Whenever a travelling wave encounters a boundary between the region it is travelling in and another region,
One, two or all of three things may happen.

Absorption of the wave

Transmission of the wave from one region to the next

Reflection of the wave back into the first region

 

Often one of these predominates - you should look up 'total internal reflection'

 

Add this to swansont's question

[swansont]

59 minutes ago, studiot said:

 Often one of these predominates - you should look up 'total internal reflection'

TIR is only possible when going from a higher index to a lower index, so I don't see how this is related to the question.

[Sigmarus]

Sorry!I honestly have not much idea what you guys are talking about :/.I'm pretty sure the reflection would be "diffused".But the liquid is transparent though.

[DrP]

They are leading you on the right track.

What happens at the surface of the liquid when it is still and the light hits it? What does the reflection look like?

What happens on the surface of the liquid when it is agitated? What is this going to do to the reflection?  

 

As Studiot suggested - the light can go straight through, it can reflect or it can be absorbed. Much of this depends on the incident angle of the incoming light. What happens to the incident angle of the light on the surface if the water is agitated?

[Sigmarus]

Well if light hits a smooth surface,it will be reflected in a regular manmer(angle of inc=angle of refr)and if it hits a rough/agitated surface,it will be diffused and scattered.

Unfortunately that's the only thing i learnt so far about reflection.

[DrP]

yes - the surface becomes wavy so now, instead of reflecting evenly, the image is distorted/scattered depending upon how much or how severe the agitation is. At low agitation the image might be a little blurred..  at high levels of agitation you might see very little of the original image. This is because the incident light rays are now reflecting off in lots of different directions depending upon how mixed and wavy the surface is.  Some might pass straight through now rather than reflecting at all due to the angle at which they hit the surface of the liquid.

Maybe there is more to it than that  -  the others can take it further if there is. That's about all I've got on that - I think it is just as simple as it sounds. Reflect of a smooth surface and you get a clear image...  reflect of a slightly agitated surface and get some blurring...  reflect of a highly agitated wavy surface and get a highly distorted and scattered image.

[swansont]

5 minutes ago, Sigmarus said:

Well if light hits a smooth surface,it will be reflected in a regular manmer(angle of inc=angle of refr)and if it hits a rough/agitated surface,it will be diffused and scattered.

Unfortunately that's the only thing i learnt so far about reflection.

And that's it.

Depending on the kind of disturbance, you can still form a recognizable image (there are different degrees of diffuse). The irregularities of a liquid are likely to be on a scale very much larger than a wavelength, while other diffuse reflections (e.g. from a painted wall) have smaller and more irregular deviations from being flat.

You will get reflections when going from a medium of one index to another. The amount depends on the difference.

[Sigmarus]

But why is there a reflection on a transparent liquid :/?

[DrP]

Not all of it goes straight through - some can be reflected and some can be adsorbed. You will notice that, although you can see your reflection, you can also see the bottom of the bowl.

[Sigmarus]

Ahhh.So is it possible if i answer it like this:"Since the disturbance of the liquid medium caused the surface of it to be rough,a diffused reflection will occur as it reflects off the liquid medium,leading to the blur image of Martin".

Please do correct me if i'm wrong

[DrP]

not wrong.. I might try something like:

"The disturbance of the medium has caused disruption on the surface so that it is no longer smooth. There will be waves and vibration patterns across the surface causing the incident light rays to scatter at different angles to what they were when the surface was smooth. Now the reflections are being scattered by the peaks and troughs in the surface of the medium causing image distortion. The image will become more distorted and scattered the more Martin agitates the liquid."

Maybe you can come up with something better still. It's just an idea/suggestion. Writing/grammar have never been my strongest points.  

 

Edited August 3, 2017 by DrP

[Sigmarus]

Well i am only 14 years of age and i don't think it its required to write it like an english essay paragraph xD.But it won't hurt to try!

Thanks alot for everyone's contribuition!

[studiot]

1 hour ago, DrP said:

not wrong.. I might try something like:

"The disturbance of the medium has caused disruption on the surface so that it is no longer smooth. There will be waves and vibration patterns across the surface causing the incident light rays to scatter at different angles to what they were when the surface was smooth. Now the reflections are being scattered by the peaks and troughs in the surface of the medium causing image distortion. The image will become more distorted and scattered the more Martin agitates the liquid."

Maybe you can come up with something better still. It's just an idea/suggestion. Writing/grammar have never been my strongest points.  

 

Pretty good.

 

Another way to look at it is to think of the difference between glass and water.

Glass can have a smooth surface or a textured one (eg for a bathroom).

You can get some sort of reflected image from either, but it is static (doesn't move).

The water is normally smooth when static, but becomes rough on movement.

 

My first post was also looking ahead  for you in this subject.

[studiot]

To further help you,

When a surface acts like a mirror the reflection is said to be specular

The opposite is called a diffuse reflection.

https://www.google.co.uk/search?biw=1024&bih=506&q=specular+and+diffuse+reflection&oq=specular+and+diffuse&gs_l=psy-ab.1.0.0l4.14531.22139.0.24698.24.23.0.0.0.0.558.4581.0j8j6j1j1j2.18.0....0...1.1.64.psy-ab..8.16.3409...0i13k1j0i7i30k1j0i8i10i30k1j0i67k1.5EBd8fQU5xg

[Sigmarus]

Thank you

[rosadaniels]

Yes, engagement with homework is undoubtedly important

[ellan108]

If you'd read this notes https://www.studocu.com/en/document/university-of-technology-sydney/medical-imaging/lecture-notes/lecture-notes-lecture-refraction-of-light/298991/view?has_flashcards=0 you'd found some useful thoughts on this theme)

 

[swansont]

On 8/3/2017 at 9:26 AM, DrP said:

Not all of it goes straight through - some can be reflected and some can be adsorbed. You will notice that, although you can see your reflection, you can also see the bottom of the bowl.

Absorbed. (adsorption is a different effect. Light will never be adsorbed.)

[studiot]

18 minutes ago, swansont said:

Absorbed. (adsorption is a different effect. Light will never be adsorbed.)

Good catch +1