Background
A ray of light is the perpendicular light drawn from one point to another in the direction of wave front of the light. Ray optics describes about the behaviour of light when strikes with different medium. It describes about reflection, refraction and total internal reflection.
Initial Questions
What is the behaviour of light when it pass through different medium?
What is the role of ray optics in data transmission?
What is polarization of light?
- Why light reflects when it hits different materials?(Note) http://scienceline.ucsb.edu/getkey.php?key=3903
- The roles of molecules in different materials to refelect light.
Selected problem
What is the behaviour of light when it pass through different medium?
My explanation (original hypothesis)
Light is an electromagnetic wave which can travel through vacuum carrying radiant energy called photon. Therefore light is both particle as well as wave.
When the ray of light coming from one medium strikes to a smooth surface, the light is reflected back towards the same medium. This is called reflection of light. The law of reflection states that the angle made by the incident ray at the point of incidence with the normal is equal to the angle made by reflected ray with the normal.
Reflection occurs in the same medium when the light cannot pass through the surface. The incident ray and the reflected ray both have speed. But when the ray of light travelling from fast medium enters to a slow medium or slow to fast medium the speed of light changes the ray of light bends towards the normal and vice versa. This bending of light when it enters to certain medium is called refraction of light.
When the incident angle is higher than the critical angle the light bounds back and there is no refraction. This phenomenon of bouncing back of the light when travelling from denser to less dense medium is called total internal reflection. There is no loss of incident rays, as the whole rays are bounced back.
Finding more information
As shown in the above figure, the incident ray (initial ray coming towards the surface) strikes on the surface of the plane mirror and bounce back to the same medium making some angle with the normal ( perpendicular line drawn at the point of incident). This phenomenon is called reflection of light.
According to the law of reflection,
Incident angle = reflected angle
When the light passes through the rare medium to the denser medium the ray of light bends towards the normal which is called refraction of light. This is the reason which makes it difficult to figure out the position of object in water. The refraction of light makes the object to appear nearer than its actual distance. But when the ray of light pass from denser to rarer medium the light bends away from the normal.
The refraction of light is also described by Snell’s law. Snell’s law states that the ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of phase velocities in the two media or equivalent to the reciprocal of the ratio of the indices of refraction:
The above figure shows the ray of light passing from slow speed medium to fast speed medium. The ray of light starts bending as the incident angle increases. The bigger the incidence angle bigger will be the refraction of light until the refraction angle is 90°. This angle is called critical angle. Further increase in the incidence angle cause all the light to bounce back toward the same medium causing no refraction. This is called total internal reflection where there is no loss of incident ray.
References
Cold atom technology for Quantum physics.[Online]
URL: http://www.physicsclassroom.com/class/refrn/Lesson-3/Total-Internal-Reflection.
About Doppler cooling effect. [Online]
URL: www.phys.ens.fr/~dalibard/publi2/laser_cooling.pdf
About new innovative progress and future of cold atom technology.[Online]
URL: http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html
About ray optics.[Online]
URL:https://www.youtube.com/watch?v=AFdwZtmQ2ZY
Information about reflection and refraction.[Online]
URL: Https://spie.org/Documents/Publications/00%20STEP%20Module%2003.pdf
Information about total internal reflection [Online]
URL: http://www.cyberphysics.co.uk/topics/light/TIR.htm
Information about refractive index.[Online]
URL: http://en.wikipedia.org/wiki/Refractive_index