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Thin Films Nelson: 10.4 + 10.5. Who is Roy G. VIB?. Dating Tip #2. Going to the zoo or the park/forest Did not take bio classes? No problem physics always give you plenty to talk about. Understanding Thin Films.
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Thin Films Nelson: 10.4 + 10.5
Dating Tip #2 • Going to the zoo or the park/forest • Did not take bio classes? No problem physics always give you plenty to talk about
Understanding Thin Films • Interference between light waves is the reason that thin films, such as soap bubbles, show colorful patterns. • It is the interference of light waves reflecting off the top surface of a film with the waves reflecting from the bottom surface
Understanding Thin Films • Reflected waves experience a 180° phase shift (half a wavelength) when hitting a higher n medium (think grade 11 fixed-end reflections of pulses) • Refracted waves travel through the thin film and reflect off the lower medium, either changing phase (if n is larger still) or not. • Both of these effects combine to yield either constructive or destructive interference for specific wavelengths.
Reflection Off a Thin Films Note: the wavelength used to describe the thickness of film is that of light in the film
Reflection Off a Thin Films • Sample Problem 1: • In summer months, the amount of solar energy entering a house should be minimized. Window glass is made energy-efficient by applying a coating to maximize reflected light. Light in the midrange of visible spectrum (at 568 nm) travels into energy efficient window glass. What thickness of the added coating is needed to maximize reflected light and thus minimize transmitted light?
Transmission through Thin Films Note: the wavelength used to describe the thickness of film is that of light in the film
Transmission Through Thin Films • Sample Problem 2: • Semiconductors, such as silicon, are used to fabricate solar cells. These cells are typically coated with a thin, transparent film to reduce reflection losses and increase the efficiency of the conversion of solar energy to electrical energy. Calculate the minimum thickness of the film required to produce the least reflection of light with a wavelength of 5.50 x 10-5 m when a thin coating of silicon oxide (n=1.45) is place on silicon (n=3.50)