Physical Optics and Light Theories Quiz

Study Notes

Light travels in straight lines through empty space.
Light travels at a velocity of 3x10¹⁰ cm/sec, independent of color and temperature of the source.
Light is a form of energy.
Different colors in white light have different refractive indices in a given medium (like glass).
Light's nature is described by the Huygens wave theory (Huygens Principle), where each point on a wavefront at any instant acts as a source of secondary wavelets. The envelope of these secondary wavelets determines the subsequent position of the wavefront.

Newton assumed light is composed of tiny particles (corpuscles).
The corpuscles travel in straight lines with a limited velocity (3x10¹⁰ cm/sec).
The theory couldn't explain interference and polarization phenomena.

For observable interference, the intensity at regions of destructive interference must remain zero, and that at regions of constructive interference must remain maximum.
Coherent sources (produced from the same source) are necessary ; the phase difference between the sources must be constant with time.

The light must be monochromatic (of a single wavelength).
The interfering sources must travel in the same direction, or at a minimal angle to each other.

The superposition of two or more wave trains on a particle in a medium results in a displacement due to the superposition of all the wave trains.
Each wave train retains its individual characteristics, acting as if others are absent.

Demonstrated interference of light using a point source and two closely spaced pinholes as separate light sources.
Bright and dark fringes are created on a screen. The bright fringes result from crest-crest or trough-trough superposition (constructive interference), and the dark fringes from crest-trough superposition (destructive interference).