Two total internal reflection examples

[guardians]

Homework Statement

-Behind a glass container with water, there is a candle. The container is paralelopiped - shaped. What is the image that the viewer is going to see, if the eye is set like so, that he watches the candle with an angle greater than the angle of total reflection?
-Hold a metal spoon over a candle and bring it into a container with water. The spoon won't look burnt. What's the reason?

Homework Equations

None - conceptual questions.

The Attempt at a Solution

-I am fairly sure that since he watches at an angle greater than the angle of total reflection, he will see the image of the cangle on the surface of the water, rotated 90 degrees. Am I right?
-I really can't put my mind into this one. I think that it has something to do with the different refraction indices of water and air - but I still don't see how this could affect the coloring - some light rays would still get to the burnt parts - and absorb the same frequencies - so the same color will remain... A little help?

 

[anathema]

Hello, thank you for your post. I can provide some insight into these questions.

For the first question, you are correct in thinking that the viewer will see the image of the candle on the surface of the water, rotated 90 degrees. This is because when light passes from a denser medium (in this case, water) to a less dense medium (air), it is refracted away from the normal (an imaginary line perpendicular to the surface). When the angle of incidence (the angle at which the light hits the surface) is greater than the critical angle (the angle at which total internal reflection occurs), the light is completely reflected back into the water, creating an image of the candle on the surface. This phenomenon is known as total internal reflection.

For the second question, the reason the metal spoon won't look burnt when placed in water is due to the difference in refractive indices between water and air. When light passes from air to water, it is refracted towards the normal, causing objects to appear closer than they actually are. This is why objects in water appear larger and closer to the surface. The metal spoon is not actually burnt, but it appears to be due to the refraction of light. This is also why objects in a glass of water appear to be bent or distorted - the light is being refracted as it passes from the air to the water.

I hope this helps to clarify these concepts for you. If you have any further questions, please don't hesitate to ask. Keep up the good work!

 

[Moetasim]

Your understanding of the first example is correct. When the eye is set at an angle greater than the angle of total reflection, the viewer will see the image of the candle on the surface of the water, rotated 90 degrees. This is because at this angle, total internal reflection occurs at the interface between the water and the glass container, causing the light rays to reflect off the water's surface and create the image.

For the second example, the reason the spoon won't look burnt is due to total internal reflection at the interface between the water and the spoon. When the spoon is held over the candle, it heats up and creates a layer of hot air around it. This layer of hot air has a lower refractive index than the surrounding water, causing total internal reflection to occur at the interface between the water and the spoon. This means that the light rays from the candle are not able to reach the spoon's surface and create the image of the burnt spoon. Instead, the viewer sees the reflection of the water's surface on the spoon, making it appear as if it is not burnt.