geomoptics1RR

geomoptics1RR - What is (visible) light? Light the visible...

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1 eometrical Optics 1 Geometrical Optics 1 Reflection and Refraction of Light What is (visible) light? Light – the visible portion of the electromagnetic ectrum spectrum Colours: red, orange, yellow, green, blue, violet A travelling electromagnetic wave, made up of oscillating electric and magnetic fields, that are utually perpendicular mutually perpendicular Moves at speed of v = c = 3 x 10 8 m/s in vacuum or air Electromagnetic Waves The (electric) and agnetic) fields are E B (magnetic) fields are perpendicular to each other Both fields are perpendicular to the irection of motion direction of motion Therefore, EM waves are transverse waves The EM Spectrum Visible light is a small portion of p the spectrum Different regions of spectrum are distinguished by frequency or wavelength v = ƒ λ for waves, (c = f ¸ in vacuum/air)
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2 Notes on The EM Spectrum Radio Waves sed in radio and television communication systems Used in radio and television communication systems Microwaves Wavelengths from about 1 mm to 30 cm Well suited for radar systems i li ti Microwave ovens are an application Notes on the EM Spectrum, 2 Infrared waves correctly called “heat waves” Incorrectly called heat waves Produced by hot objects and molecules Readily absorbed by most materials Visible light Part of the spectrum detected by the human eye Most sensitive at about 560 nm (yellow-green) 1 nanometer = 10 -9 m Notes on the EM Spectrum, 3 Ultraviolet light Covers about 400 nm to 0.6 nm Sun is an important source of UV light Most UV light from the sun is absorbed in the stratosphere by ozone X-rays ost common source is acceleration of high- nergy Most common source is acceleration of high energy electrons striking a metal target Used as a diagnostic tool in medicine Notes on the EM Spectrum, 4 Gamma rays mitted by radioactive nuclei Emitted by radioactive nuclei Highly penetrating and cause serious damage when absorbed by living tissue
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3 Geometric Optics – Using a Ray Approximation Light travels in a straight-line path in a homogeneous medium until it encounters a boundary between two different media The ray approximation is used to represent beams of light; a ray is an imaginary line drawn along the direction of travel of the light beams Ray Approximation A wave front is a surface passing through pg g points of a wave that have the same phase and amplitude The rays, corresponding to the direction of the ave motion are wave motion, are perpendicular to the wave fronts Geometrical Optics: everyday experience Examine interaction of light of wavelength ¸ with gg objects of size d >> ¸ Light travels in straight lines called rays , with wavefronts ? to rays Objects cast sharp shadows Reflection & Refraction of Light a ray of light, the incident ray , travels in a medium
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geomoptics1RR - What is (visible) light? Light the visible...

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