^Convex mirror & Concave lens
A convex mirror has Inner or depressed side polished. A concave lens is thick near edges & thin near the center. They have following common features
^Concave mirror & Convex lens
A concave mirror has outer or bulged side polished. A convex lens is thick near center & thin near the edges. They have following common features
^Plane mirror
1. Image formed by a plane mirror is virtual, erect, undiminished, unmagnified, behind the mirror such that both the object & image are at equal distances from the mirror.
2. A plane mirror forms real image for a virtual object.
^Spherical aberration
The various rays in a wide beam falling on a concave mirror of large aperture after reflection don’t meet at a single focus, marginal rays get focused somewhere between F & F while paraxial between C & F , consequently the image formed is not bright & single but a large no. of blurred images are produced.
In order to minimize the spherical aberration defect we shall use
(a) Objects with low heights
(b) Paraxial incident rays
(c) Mirrors of small aperture (called parabolic mirror, used as reflectors of head lamps of vehicles).
^Paraxial & marginal rays
In a wide beam of incident rays the rays travelling close to principal axis are called paraxial & the rays away from principal axis are called marginal.
^Law of reflection
Using law of reflection we can say
(a) For normal incidence (i.e. i = 0) rays of light reflect back & retrace the path.
(b) Light ray passing through pole along principal axis of a mirror of any kind retraces its path i.e. suffers a deviation of 1800.
(c) Light rays parallel to principal axis passes through the focus after reflection.
(d) Light rays through focus become parallel to the principal axis after reflection.
(e) Light ray incident at some angle to principal axis emerges at equal angle with the principal axis after the reflection.
^Reflection of light
^Visible light
Visible light is a mixture of photons λ = 380 nm (violet) to 780 nm (violet) in appropriate proportion. Colour of light is determined by its frequency & not wavelength.
^Energy of a photon
Energy ‘E’ of a photon depends upon its frequency ‘f’ or wavelength ‘λ’ & is described by Max Planck quantum radian law
[called energy condition
Energy of visible light is greater than that of infra red but smaller than ultraviolet. Red colour photons have maximum wavelength thus are least energetic. Also violet colour photons have minimum wavelength thus are most energetic.
^Optical frequencies
Using the relation c = f λ, with c = 3 x 108 m /s & λ = 380 nm to 780 nm we can check that the optical frequencies are of the order of 1015 Hz.
Call 9872662552