A wavefront is the locus of all points that are in the same phase of vibration.
A ray is an imaginary line that represents the direction of wave propagation.
It is always perpendicular to the direction of wave propagation.
It is always perpendicular to the wavefront.
Examples: Plane wavefront, spherical wavefront.
Used to represent light beams in geometrical optics.

A racing track is built around an elliptical ground whose equation is given by \[ 9x^2 + 16y^2 = 144 \] The width of the track is \(3\) m as shown. Based on the given information answer the following: 
(i) Express \(y\) as a function of \(x\) from the given equation of ellipse.
(ii) Integrate the function obtained in (i) with respect to \(x\).
(iii)(a) Find the area of the region enclosed within the elliptical ground excluding the track using integration.
OR
(iii)(b) Write the coordinates of the points \(P\) and \(Q\) where the outer edge of the track cuts \(x\)-axis and \(y\)-axis in first quadrant and find the area of triangle formed by points \(P,O,Q\).