Phy107Lect16

Phy107Lect16 - HW#6 Chapter 10 Concept: 19, 16, 20, 28, 34...

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From Last Time… • HW#6 Chapter 10 Concept: 19, 16, 20, 28, 34 Problems: 4, 6 Range of visible light from 400 nm to 700 nm Eye interprets different wavelengths as different colors but has only three ‘sensors’, cones S, M, L with overlapping sensitivities. Lets colors be described as combination of three ‘primaries’ This makes a ‘color space’, colors can be described as amount of primaries needed. Most methods of generating colors have a ‘gamut’, a limited range of possible colors that in general to not contain pure spectral colors.

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Relativity and Modern Physics • Physics changed drastically in the early 1900’s • New discoveries — relativity and quantum mechanics • Relativity Changed the way we think about space and time • Quantum mechanics Has led to multitude of technological achievements
Relativity and frames of reference • Frame of reference The coordinate system in which you observe events. e.g. The room around you. You judge how fast a thrown ball goes by its velocity relative to some stationary object in the room. You judge how high a thrown ball goes by distance from the floor, ceiling, etc. • Different frames Suppose you are on the van Galder bus to Chicago driving at 60 mph, and throw the ball. From your seat on the bus, the speed of ball is the same as in this classroom. To the major league scout on the side of the road, your 40 mph fastball has become 100 mph.

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Preferred reference frame • Who is correct? – You wouldn’t last long in the majors. – But that’s because the important velocity in a baseball game is the relative velocity of ball with respect to pitcher. But what is the absolute velocity of the ball?
Relative velocities • Earth spins on its axis One rotation in (24 hrs)(60 min/hr)(60 sec/min)=86400 sec Point on surface moves 2 π R E in one rotation. Surface velocity = 2 π (6.4x10 6 m)/86400 sec = 465 m/s • Earth revolves around sun One revolution in (365 days)(86400 sec/day)=3.15x10 7 sec Earth velocity = 2 π (1.5x10 11 m)/ 3.15x10 7 sec=3x10 4 m/s • Sun moves w/ respect to center of milky way galaxy

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Galilean relativity • Absolute velocity not clear, but we can seemingly agree on relative velocities. – In all cases the ball moves 40 mph faster than I do. • This is an example of Galilean relativity: The laws of mechanics are the same in all inertial frames of reference Inertial Frame: reference frame moving in straight line with constant velocity.
Galilean relativity: example Experiment performed – in laboratory at rest with respect to earth’s surface – in airplane moving at constant velocity …must give the same result.

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This note was uploaded on 01/05/2012 for the course PHYS 107 taught by Professor N/a during the Spring '08 term at Wisconsin.

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Phy107Lect16 - HW#6 Chapter 10 Concept: 19, 16, 20, 28, 34...

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