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# Physics 504 chapter 1 geometric optics

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• Chapter Slide
• Reflection
• Pinhole camera
• ### Transcript

• 1. Physics 504 Chapter 1 Geometric Optics
• 2. Alexander Pope• Nature and Nature’s laws lay hid in night;• God said, Let Newton be!• And all was light.• Epitaph intended for Sir Isaac Newton
• 3. Light• Light is an electromagnetic disturbance whose propagation allows the transportation of light energy.• Light is considered to travel as a wave AND as particle or photon.• As a wave, light has different frequencies or cycles per second (cps)• The unit of frequency is a hertz (Hz).
• 4. My Brain Hertz• Frequency = # Cycles / Time (s)• Period = Time (s) / # Cycles• So, Period = 1 / Frequency• Wave Velocity = Wavelength x Frequency• v (m/s) = λ (lambda) (m) x f (Hz)• For electromagnetic waves:• c = λf• c (speed of light) = 3x10 8 m/s
• 5. Example• If a water tap drips 150 times a minute, and the distance between the waves is 6 cm, what is the velocity of the waves?• Wave frequency = # cycles / time• = 150/60s• = 2.5 Hz• Wave velocity, v = λf• = 0.06 m x 2.5 Hz• = 0.15 m/s
• 6. Speed of light• Light travels at a definite speed (c);• c = 3x108 m/s = 300000 km/s• Distance = speed x time• Calculate the distance (km) travelled in: • 1 minute • 1 hour • 1 day • 1 year - 365.25 days – 1 lightyear
• 7. Types of Light Sources• Incandescent: materials emit light when heated to a high temperature. E.g. Stove element, light bulb• Luminescent: light is emitted through a reaction with little or no heat released. E.g . Glow sticks, fire flies are bioluminescent• Fluorescent: materials release light because of the absorption of high energy radiation. E.g. fluorescent light bulbs• Phosphorescent: similar to fluorescent except that the light continues to be emitted after the source of radiation has been removed. E.g. glow-in-the-dark toys
• 8. Light objects• Luminous: materials that can emit light. E.g. the sun, stars• Non-luminous: objects that can only be seen by reflected light. E.g. the moon
• 9. Light Phenomena• Reflection: light rays bouncing off a face• Refraction: light rays bending• Diffusion: light scattering off dust• LASER = Light Amplification by the Stimulated Emission of Radiation• Diffraction: light spreading out• Absorption: light absorbed into objects• Dispersion: light separating into colours
• 10. Transmission of light• Recti-Linear propagation: light travels in straight lines;• Ray: the path taken by light energy;• Ray diagrams: pictures that show the paths of light rays;• Diverge: light rays become farther apart;• Converge: light rays come closer together;• Parallel rays: rays that travel the same distance apart;• Speed of light: c = 3x108 m/s
• 11. Pinhole Camera Image
• 12. Pinhole camera• Pinhole cameras demonstrate that light travels in straight lines;• An image is formed inverted vertically and horizontally on the back of the camera• The image willbe inverted,smaller and real.
• 13. Pinhole camera• Magnification = height of image height of object• Or, M = h i/ h o• As well, M = distance to image distance to object• Or, M = d I/d O• So h i/ h o = d I/d O
• 14. QuestionA pinhole camera is used to show the image of a turtle on its screen as shown below.Which of the following is the image of the turtle that will appear on the screen of the pinholecamera? A) C) B) D)
• 15. QuestionAlex places a 5.00 cm tall candle 30.0 cm in front of a pinhole camera that hasa length of 50.0 cm.What is the magnification of the candle? A) 1.66 B) 0.166 C) 0.63 D) 0.1