Physics - total internal reflection of waves Flashcards
How does light act going through a denser medium than air?
When light travels from a denser medium, eg glass, to a less dense medium, eg air, the speed of the light increases and the light refracts away from the normal. The angle of refraction is greater than the angle of incidence.
What is the angle of refraction and the angle of incidence?
Angle of refraction - Angle between the normal and the refracted ray.
Angle of incidence - Angle between the normal and the incident ray.
What are the conditions for total internal reflection to occur?
-The light must be travelling from a more dense medium into a less dense medium (ie glass to air)
-The angle of incidence must be greater than the critical angle(42 degrees)
How does an optical fibre work?
Optical fibres rely on total internal reflection for their operation.
An optical fibre is a thin rod of high-quality glass. Light getting in at one end undergoes repeated total internal reflection and emerges at the other end.
Light refracts towards the normal as it enters the optical fibre. When the light hits the end of the fibre the angle of incidence is now less than the critical angle and the light refracts away from the normal into the air.
What is an endoscope? How does it work?
An instrument used in medicine to help examine the inside of the body, which uses a bundle of optical fibres to transmit the image around corners. This allows the doctor to see an image of the inside of the body clearly.
What is a CT scan? How does it work?
Traditional X-ray imaging gives a 2D view of the body from one angle. This can result in detail being obscured by other structures in the body. CT scans involve taking a range of X-ray images from various positions. These are processed by a computer to build a 3D image. This image can be manipulated in order to see the structures within the body at different layers and from different points of view.
What is better : endoscopes or CT scans?
Endoscopy is used to investigate specific areas of the body. It is less harmful than CT scans. It uses light rather than X-rays. CT scans are used to generate more overall images of the body, and are a higher risk than endoscopes due to the fact that they use X-rays.
CT scans produce 3D images of the body. Endoscopy produces 2D images of the body.
