Define the term, ‘Critical Angle’. What is meant by ‘total internal reflection’? State two essential conditions for total internal reflection to take place. With the help of a ray diagram, illustrate an application of total internal reflection. OR (a) What is meant by a ‘magnetic field’? (b) How is the direction of magnetic field at a point determined? (c) Describe an activity to demonstrate the direction of the magnetic field generated around a current carrying conductor. (d) What is the direction of magnetic field at the centre of a current carrying circular loop?
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critical angle: the angle of incidence in the denserer medium corresponding to which the angle of refraction in the rarer medium is 90 degrees
total internal reflection: When a ray of light travelling in the denser medium is incident on the surface of the rarer medium, such that the angle of incidence is greater than the critical angle for the pair of media, the ray of light is completely reflected in the denser medium, this phenomenon is called TOTAL INTERNAL REFLECTION
conditions for total internal reflection are:
1 the light ray must travel from denser medium to rarer medium
and,2 the angle of incidence must be greater than the critical angle for the pair of media
total internal reflection: When a ray of light travelling in the denser medium is incident on the surface of the rarer medium, such that the angle of incidence is greater than the critical angle for the pair of media, the ray of light is completely reflected in the denser medium, this phenomenon is called TOTAL INTERNAL REFLECTION
conditions for total internal reflection are:
1 the light ray must travel from denser medium to rarer medium
and,2 the angle of incidence must be greater than the critical angle for the pair of media
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Total internal reflection is the phenomenon which occurs when a propagated wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is greater than the critical angle, the wave cannot pass through and is entirely reflected. The critical angle is the angle of incidence above which the total internal reflection occurs. This is particularly common as an optical phenomenon, where light waves are involved, but it occurs with many types of waves, such as electromagnetic waves in general or sound waves. When a wave reaches a boundary between different materials at an angle of less than 25° with different refractive indices, the wave will in general be partially refractedat the boundary surface, and partially reflected. However, if the angle of incidence is greater (i.e. the direction of propagation is closer to being parallel to the boundary) than the critical angle – the angle of incidence at which light is refracted such that it travels along the boundary – then the wave will not cross the boundary, but will instead be totally reflected back internally. This can only occur when the wave in a medium with a higher refractive index (n1) reaches a boundary with a medium of lower refractive index (n2). For example, it will occur with light reaching airfrom glass, but not when reaching glass from air.
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