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Chapter 27 Physics
Question | Answer |
---|---|
how does light affect things? | light is the only thing you see, all visible objects either reflect or emit light, most of what we see is reflected light |
what are sources of light? | sun, lamp, candle, glowing gases |
what is transparent and opaque? | some materials let light pass through-transparent (glass, air, water) most things don't let light pass at all-opaque (wood, metal) |
what is translucent? | some things let light pass through in diffused directions (thin paper, frosted glass) |
what do scientists now agree about light? | it has a dual nature, part particle and part wave |
what are some early ideas of light? | light has been studied for thousands of years, greek philosophers thought it was particles that entered the eye and created vision others-streamers or filaments emitted from eye made contact with objects |
what did newton think? | up until the 1600s thought light was particles that traveled in straight lines |
what did huygens think? | light was waves and beams could pass through each other like waves do but people still believed newton |
what did t young do? | showed light could be spread out like waves (diffraction) and wave theory was accepted, 19th century |
what did einstein do? | photo electric effect, consists of particles (mass less bundles of electromagnetic energy packaged in bundles called photons) move as waves |
what did michelson do? | discovered speed of light to be 300,000 km/s, using spinning mirror, 1st american-nobel prize |
what did galileo do? | tried to measure speed of light with lanterns |
what did roemer do? | astronomer who studied moons of jupiter to learn about speed of light |
what is the speed of light? | universal constant "c" |
what are some speeds and times for light to travel different places? | around earth 7.5 times in one second, 8 minutes for light from the sun to reach earth, 4 years for light from the nearest star (AlphaCentauri), the distance light can travel in one year at 300,000km/s is called a lightyear |
what is the electromagnetic spectrum? | consists of radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays |
what is light? | energy that is given off by an accelerating electric charge (e-) |
how does this energy travel? | a wave that is partly magnetic and partly electric-electromagnetic wave, light is only one kind of electromagnetic wave, range-electromagnetic spectrum |
helpful hints-electromagnetic spectrum | left side longer wavelength-lower energy, right side-higher frequency, more energy |
what is the lowest frequency of light we can see? highest? | red, violet |
what speed do electromagnetic waves travel at? | they all travel at the same speed-the speed of light, but they are different in their frequencies and wavelengths |
what is infrared? | electromagnetic waves of frequencies lower than the red of visible light, heat lamps |
what is ultraviolet? | electromagnetic waves of frequencies higher than those of violet, sunburns |