Ray Optics And Optical Instruments

(a) Brewster's law states that when ordinary light is incident on a transparent surface at polarizing angle for that surface, the tangent of angle of polarisation is equal to the refractive index of the medium of surface, that is, (b) Lambert's law concerns to rate of absorption of radiation as it travels deeper into a medium. It states that the intensity of radiation falls off exponentially with distance d in the medium. (a) Brewster's law states that when ordinary light is incident on a transparent surface at polarising angle for that surface, the tangent of angle of polarisation is equal to the refractive index of the medium of surface, that is,

(b) Lambert's law concerns to rate of absorption of radiation as it travels deeper into a medium. It states that the intensity of radiation fails off exponentially with distance in the medium. (c) Law of Malus states that intensity of light coming out of analyser is proportional to the square of the cosine of the angle between the plane of analyser and polariser. (d) According to Bragg's law if a beam of -rays of wavelength is directed at a crystal with parallel crystal planes that are distance d apart, then the reflected -rays from each plane undergo interference.

Light waves do not require a material medium for their propagation. Also they travel through vacuum. metallic plate kept in the path of light rays gets heated up, showing that light involves transportation of energy. Also speed of light is which is constant.

The first idea is that for no refraction at its lateral face, angle of incidence should be greater than critical angle. Let a light ray enters at and refracted beam is . At the lateral face, the angle of incidence is . For no refraction at this face, . i.e., but

The second idea is that in . (i), the substitution for can be found from Snell's law. Now, from Snell's law, E (i) gives, Also or The maximum value of is So, or

Total internal reflection is the phenomenon of reflection of light into a denser medium from an interface of denser medium and rarer medium. The essential conditions for total internal reflection are (i) Light should travel from a denser medium to a rarer medium. (ii) Angle of incidence in denser medium should be greater than the critical angle for the pair of media in contact. We may define critical angle for a pair of media in contact as the angle of incidence in the denser medium corresponding to which angle of refraction in the rarer medium is It is represented by and its .value depends on the nature of media in contact. In total internal reflection, of incident light is reflected back into the same medium, and there is no loss of intensity. That is why images formed by total internal reflection are much brighter than those formed by mirrors or lenses.

Angular limit of resolution of eye is the ratio of wavelength of light to diameter of eye lens. Angular limit of resolution of eye ie, ...(i) If is the minimum resolution between two objects at distance from eye, then ..(ii) From Eqs. (i) and (ii), we have or ...(iii) Given, , , Substituting in E (iii), we get

Here, angle of incidence,

Angle of deviation

Power Focal length of combination of convex and concave lens is given by where and be the focal lengths of convex and concave lenses respectively. Now, Power

If a lens (made of glass) of refractive index is immersed in a liquid of refractive index , then its focal length in liquid is given by If $\mu_{g}