Chapters 22 & 23 Notes
Light – type of energy that travels as a wave and DOES NOT need a
medium (electromagnetic wave)
EM waves are produced by the vibration of electrically charged
particles. These vibrate the surrounding area causing a magnetic field.
The vibrations cause the EM waves to transfer energy known as
radiation.
Light travels 800,000 times faster than sound at 300,000,000
meters/sec or 300,000 km/sec in a vacuum. It travels slightly slower
through air, glass and other types of matter. Light takes about 8.3
minutes to get to earth from the sun because earth is 150,000,000 km
away from the sun.
Electromagnetic Spectrum – entire range of EM waves from radio waves
to gamma rays
Radio waves – longest wavelength/lowest frequencies/lowest energy
*modulation is changing frequencies or amplitudes from sound to radio
waves (AM is amplitude modulation and FM is frequency modulation)
Microwaves – part of radio waves(but have slightly higher frequencies)
used for cell phone communication, satellite transmission from space and
radar
Infrared – shorter wavelengths/higher frequencies that cause warmth on
your skin
Visible light – shorter wavelengths/higher frequencies; narrow range on
EM spectrum that can be seen
*ROYGBIV – colors of the rainbow
*White light – all colors reflected that can be separated by a prism
*Black – all colors absorbed
Ultraviolet light – shorter wavelengths/higher frequencies; comes from
the sun
*bad effects – sun damage, skin cancer, eye damage
*good effects – helps body produce vitamin D which helps body
absorb calcium, UV lamps used to kill bacteria
X rays – shorter wavelengths/higher frequencies; can pass through many
materials but not lead, which is why people wear lead aprons when
getting an X ray
Gamma rays – shortest wavelength/highest frequency; can penetrate
most materials easily
*used to treat some forms of cancer and kills bacteria in meat and
fresh fruits
Reflection – light bounces off objects
Refraction – light bends as it travels from 1 material to another due to
a change in speed (causes visible spectrum to be divided in prisms and
raindrops)
Diffraction – bending of waves around barriers or through openings
Transparent – can be seen through easily; transmits light easily
ex. glass, air, water
Translucent – can be seen through but not clearly; transmits AND
scatters light
ex. wax paper, frosted glass, glass block windows
Opaque – cannot be seen through; doesn’t transmit any light
ex. metal, wood, shades
Pigment – material that gives a substance its color by absorbing some
colors and reflecting others
Chapter 23
Plane mirror – flat surface; image is same size and right side up
Concave mirror – curved (caved) inward; can make images appear upside
down
* used in car headlights and flashlights
Convex mirror – curved outward; makes image appear right side up but
much smaller than normal
*used in stores and factories for security and side mirrors for
cars
Lens – transparent object that forms an image by refracting light waves
Convex lens – thicker in the middle than the edges; can form small
images if it’s held farther away from the object or larger images if it’s
held closer to the object
*used in magnifying glasses, camera lenses, and eyeglasses
Concave lens – thinner in the middle than at the edges; form images
smaller than the object
*used in microscopes and eyeglasses
Light bends as it enters the cornea, which is the protective covering of
the eyes. It passes through an opening called the pupil, which is
controlled by the colored part (iris). The convex lens focuses light on
the retina, which is the back of the eye. The retina has rods (dim
light) and cones (colors). The Optic nerves attached to the rods and
cones carry the information to the brain.
Nearsighted – eye is too long; can see things close up easily but not far
distances
*corrected with concave lenses
Farsighted – eye is too short; can see things far away, not close up
*corrected with convex lenses
Corrective surgery uses lasers to reshape the cornea so the light is
refracted on the retina correctly.
Optical instruments – devices that use lenses and mirrors to help people
make observations
Camera – most like the human eye; has lens, shutter, and
aperture(opening)
Telescopes – used to see distant objects
*refracting - use lenses to collect light
*reflecting – use mirrors to collect light
Microscopes – magnify images by using 2 convex lenses and an eyepiece
lens
Laser – intense light of only 1 color and 1 wavelength
*used to cut some materials, surgery, and to read CD’s(light
from the laser is reflected off the pattern on the CD and converted to
a sound wave)