IV. Optics Nature of light. Spectrum of electromagnetic waves. Wavelength decreases  Frequency increases  Note: 1 nanometer = 10-9 meter

A. Geometric optics 1. Wave front and rays 2. Reflection wave fronts 1. Wave front and rays normal to surface 2. Reflection in out diffuse reflection 3. Refraction: Snell’s Law index of refraction: Example: n1 n2 n3

Example:

Example: Equilateral triangle

4. Total internal reflection Example:

Example: A ray of light is incident in air on a block of a transparent solid whose index of refraction is n =1.38. What is the largest angle θ1 for which total internal reflection will occur at the vertical face (point A)? A n=1.38 Example: α α n=1.52 α

4a. Applications of total internal reflection 1) Binoculars often use total internal reflection; this gives true 100% reflection, which even the best mirror cannot do. 2) Fiber optics. Light will be transmitted along the fiber even if it is not straight An image can be formed using multiple small fibers The typical value of the index of refraction for optical fibers: for the core n=1.48 for the cladding n=1.46

5. Plane mirror do di O O do di do = di ho = hi Image in plane mirror: virtual erect the same size 6. Comments about objects and images created by different optical instruments: curved mirrors, lenses and their combinations Image: real or virtual erect or inverted lager, smaller, or the same size as the object