Physics in Depth

A prism is a transparent refracting medium bounded by two plane surfaces meeting each other along a straight edge. In the figure below, AB and AC are the refracting surfaces and ∠BAC is the angle of prism. Consider a prism placed in air and a ray PQ be inicident on a refracting surface AB. The ray is then refracted along QR. The angle of incidence and angle or refraction are 'i' and 'r 1 ' here respectively. The ray QR is then incident upon AC. Here, the light goes from optically denser medium to an optically rarer medium. If the angle of incidence in the denser medium 'r 2 ' is not greater than the critical angle, the ray is refracted (emerge out) in air along RS. The angle 'e' is the angle of emergence. If the prism were not present, the incident ray would have passed undeviated along PQTU. Because of the prism, the final ray goes along RS. The angle UTS=δ is called the angle of deviation. When the angle of inc

When a light ray is incident on a surface separating two transparent media, the ray bends at the time of changing the medium. The angle of incidence 'i' and the angle of refraction 'r' follow Snell's law. When light ray travels from rarer to denser medium, it bends towards the normal & when light ray travels from denser to rarer medium, it bends away from the normal. A point on the base of the beaker slightly appears to be raised from the real point, this is called apparent shift which is due to the refraction of light. For certain angle of incidence in the denser medium, the angle of refraction will be 90 degree in the rarer medium. This specific angle of incidence in the denser medium is the critical angle. For angle of incidence greater than the critical angle (in the denser medium), the light will be totally internally reflected in the same medium. This is called the 'total internal reflection of light'.  Click on  Refraction  to fi