Total Internal Reflection in Glass prism Question?

In summary, the periscopes on submarines are designed to achieve total internal reflection so that the crew can see inside. This happens when the angle of incidence is greater than the critical angle, and only happens when light travels slowly through the first medium.
  • #1
Mohd95
4
0
Question about Total Internal Reflection?
My textbook says that for total internal reflection to occur 2 conditions need to be met. Light is traveling more slowly in the first medium than the second medium and no.2 is the angle of incidence must be large enough for no refraction to occur.

My question is about the first condition why does total internal reflection occur when a light ray is shined through a Glass Isoceles Right Angle Prism like the one in old submarine periscopes. I mean isn't light traveling from air to glass therefore entering from a less dense medium into a more dense medium meaning light is faster in the first medium than the second medium.

My second question is it also asks me : Why does total internal reflection occurs only when light travels slowly through the first medium than in the second and not the other way around. Explain

I need a good answer please and I am in Grade 10 so don't make it very complex

Heres the link of the prism I am alking about: http://www.gcse.com/waves/images/periscope.gif

Also Sources would be appreciated.
 
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  • #2
Mohd95 said:
My question is about the first condition why does total internal reflection occur when a light ray is shined through a Glass Isoceles Right Angle Prism like the one in old submarine periscopes. I mean isn't light traveling from air to glass therefore entering from a less dense medium into a more dense medium meaning light is faster in the first medium than the second medium.

In your link, you can see that the total internal reflection takes place only at the hypotenuse face of the prism (both figures). You are right about light entering from rarer to denser medium (air to glass), but at the site of reflection, you can observe that light tends to go from glass to air (denser medium to rarer medium). If the angle of incidence there is greater than the critical angle, then total internal reflection takes place. The periscopes are manufactured keeping all these conditions in mind.

Mohd95 said:
My second question is it also asks me : Why does total internal reflection occurs only when light travels slowly through the first medium than in the second and not the other way around. Explain

When light travels from denser to rarer medium (slowly through the first than in the second), it bends away from the normal. With increasing angle of incidence, angle of refraction also increases. There comes a time when the refracted ray just grazes the plane of separation. Any angle of incidence greater than this will lead to total internal reflection.

If light travels from rarer to denser medium, it bends towards the normal. Even if you increase the angle of incidence, there is no case possible when the light grazes the plane of separation. So no total internal reflection is possible here.

I hope it is clear.
 
  • #3
Thanx a lot man
 

1. How does total internal reflection occur in a glass prism?

Total internal reflection occurs in a glass prism when a light ray traveling through the prism hits the boundary between the glass and air at an angle greater than the critical angle. This causes the light ray to be completely reflected back into the glass, rather than refracted out of the prism.

2. What is the critical angle for total internal reflection in a glass prism?

The critical angle for total internal reflection in a glass prism is determined by the refractive index of the glass and the surrounding medium (usually air). It can be calculated using the formula sinθc = n2/n1, where θc is the critical angle, n2 is the refractive index of the surrounding medium, and n1 is the refractive index of the glass.

3. Can total internal reflection occur in materials other than glass?

Yes, total internal reflection can occur in any material with a higher refractive index, such as water or diamond. However, it is most commonly observed in glass due to its high refractive index and the ability to shape it into a prism.

4. How is total internal reflection used in practical applications?

Total internal reflection is used in a variety of practical applications, including fiber optics for telecommunication and medical imaging, prisms in binoculars and cameras, and reflectors in traffic signs and road markings.

5. What is the difference between total internal reflection and regular reflection?

The main difference between total internal reflection and regular reflection is that total internal reflection occurs when a light ray is completely reflected back into the same medium, while regular reflection occurs when a light ray is reflected at an angle equal to the incident angle. Total internal reflection only occurs when the incident angle is greater than the critical angle, while regular reflection can occur at any angle.

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