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Compare the characteristics of sound, light, and seismic waves (e.g.,transverse/longitudinal, travel through various media, relative speed)
- sound:
- longitudinal - pulse moving down slinky, air particles move back and forth
- travel through gas, liquid and solids but won't carry in a vacuum
- travels through air about 340 m/s
- light:
- transverse - medium moves at right angles to the direction of the wave
- travels at 3 x 108 m/s
- seismic:
- travel through Earth
- can be transverse or longitudinal
- longitudinal - P waves, several km per second through crust
- transverse - S waves, somewhat slower
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Explain that energy is transferred by waves without mass transfer and provide examples
- mechanical waves are variations that travel through a medium carrying energy
- as the waves travel through the medium they locally displace some particles in the medium from their normal position
- those particles then oscillate
- example - in a sound wave, air particles oscillate back and forth, creating alternating bands of low and high pressure
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Explain how lenses are used in simple optical systems, including the camera, telescope, microscope, and the eye
- converging lens:
- outside the focal point - real and inverted
- inside the focal point - virtual and right-side up
- at the focal point - no image
- diverging lens:
- the image will be on the same side of the lens, virtual, reduced and upright
- the eye:
- focuses light using the cornea and lens - both converging lenses
- lens can change shape or thickness to change the distance of the focal point - adjusts to different diverging rays of light
- camera:
- converging lens creates real image on the sensor or film
- telescope:
- two converging lenses - large one at the opening to collect light, small one in the eyepiece to bring the image to the eye
- focal point for both lenses is at the same place
- microscope:
- focal length of the objective lens is small
- eyepiece focal length is long
- the object is outside the focal point of the objective lens
- the image formed by the objective is at the focal point of the eyepiece
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Explain and apply the laws of reflection and refraction
- reflection: the angle of incidence is equal to the angle of reflection
- angles are measured with respect to the normal of the reflecting surface
- refraction: the changing of direction and speed of light when it goes from one medium to another
- when entering new medium, angle is deviated toward the normal if the new medium has a higher index of refraction
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Compare transmission, reflection, and absorption of light in matter
- transmission: when light passes through matter
- reflection: reflected pulse is upside down, phase change of 180
- absorption: energy is converted to heat
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