Download chapter 23 notes for eighth grade physical science

CHAPTER 23 NOTES FOR EIGHTH GRADE PHYSICAL
SCIENCE
SCIENTISTS DESCRIBE OBJECTS THAT PRODUCE VISIBLE LIGHT AS BEING
LUMINOUS.
SCIENTISTS DESCRIBE A VISIBLE OBJECT THAT IS NOT A LIGHT SOURCE
AS BEING ILLUMINATED.
LIGHT PRODUCED BY A HOT OBJECT IS CALLED INCANDESCENT LIGHT.
SOURCES OF INCANDESCENT LIGHT ALSO RELEASE A LARGE AMOUNT OF
THERMAL ENERGY.
FLOURESCENT LIGHT IS VISIBLE LIGHT EMITTED BY A PHOSPHOR
PARTICLE WHEN IT ABSORBS ENERGY SUCH AS ULTRAVIOLET LIGHT.
THE VISIBLE LIGHT EMITTED BY ATOMS OF CERTAIN GASES SUCH AS NEON, WHEN THEY ABSORB
AND THEN RELEASE ENERGY IS CALLED NEON LIGHT.
VAPOR LIGHT IS PRODUCED WHEN ELECTRONS COMBINE WITH GASEOUS METAL ATOMS.
A PLANE MIRROR IS A MIRROR WITH A FLAT SURFACE. WHEN YOU LOOK IN A PLANE MIRROR, YOUR
REFLECTION IS UPRIGHT AND IS THE SAME SIZE AS YOUR ARE. IMAGES IN PLANE MIRRORS ARE
REVERSED LEFT TO RIGHT.
WHEN LIGHT RELFLECTS OFF THE MIRROR, YOUR BRAIN INTERPRETS THE REFLECTED LIGHT AS IF
IT TRAVELS IN A STRAIGHT LINE FROM BEHIND THE MIRROR.
A VIRTUAL IMAGE IS AN IMAGE THROUGH WHICH LIGHT DOES NOT ACTUALLY TRAVEL. THE IMAGE
FORMED BY A PLANE MIRROR IS A VIRTUAL IMAGE.
MIRRORS THAT ARE CURVED INWARD, SUCH AS THE INSIDE OF A SPOON, ARE CALLED CONCAVE
MIRRORS.
LIGHT BEAMS ENTERING THE MIRROR PARALLEL TO THE OPTICAL AXIS ARE REFLECTED THROUGH
A SINGLE POINT CALLED THE FOCAL POINT.
THE DISTANCE BETWEEN THE MIRROR'S SURFACE AND THE POCAL POINT IS CALLED THE FOCAL
LENGTH.
CONCAVE MIRRORS ALSO FORM VIRTUAL IMAGES, BUT THEY CAN FORM REAL IMAGES TOO.
A REAL IMAGE IS AN IMAGE THROUGH WHICH LIGHT ACTURALLY PASSES. A REAL IMAGE CAN BE
PROJECTED ON TO A SCREEN, A VIRTUAL CANNOT.
IF AN OBJECT IS PLACED AT THE FOCAL POINT OF A CONCAVE MIRROR, NO IMAGE WILL FORM.
A CONVEX MIRROR IS A MIRROR THAT CURVES OUT TOWARD YOU. ALL IMAGES FORMED BY
CONVEX MIRRORS ARE VIRTUAL, UPRIGHT AND SMALLER THAN THE ORIGINAL OBJECT. (CAR
MIRROR)
A LENS IS A CURVED, TRANSPARENT OBJECT THAT FORMS AN IMAGE BY REFRACTING, OR BENDING
LIGHT.
A CONVEX LENS IS THICKER IN THE MIDDLE THAN AT THE EDGES.
WHEN LIGHT RAYS ENTER A CONVEX LENS, THEY REFRACT TOWARD THE CENTER.
A CONCAVE LENS IS THINNER IN THE MIDDLE THAN AT THE EDGES. LIGHT RAYS ENTERING A
CONCAVE LENS PARALLEL TO THE OPTICAL AXIS ALWAYS BEND AWAY FROM EACH OTHER TOWARD
THE EDGES OF THE LENS; THE RAYS NEVER MEET.
YOU SEE LIGHT THROUGH A SERIES OF STEPS THAT INVOLVES THE VARIOUS PARTS OF THE EYE
AND THE BRAIN.
1. LIGHT ENTERS THE EYE THROUGH AN OPENING CALLED THE PUPIL
2. THE COLORED AREA SURROUNDING THE PUPIL, CALLED THE IRIS CONTROLS THE AMOUNT OF
LIGHT.
3. A LENS IN THE EYE REFRACTS THE LIGHT AND MAKES IT CONVERGE ON THE RETINA.
4. THE RETINA IS MADE OF LIGHT-SENSITIVE NERVES THAT TRANSFER THE IMAGE TO THE BRAIN.
A NEARSIGHTED PERSON CAN SEE OBJECTS CLEARLY ONLY IF THE OBJECTS ARE NEARBY.
A FARSIGHTED PEROSN CAN SEE FARAWAY OBJECTS CLEARLY, BUT OBJECTS NEARBY LOOK
BLURRY.
COLOR DEFICIENCEY OCCURS WHEN THE CONES IN THE RETINA DO NOT RECEIVE THE RIGHT
INSTRUCTIONS.
THE THREE TYPES OF CONES ARE NAMED FOR THE COLORS THEY DETECT MOST- RED, GREEN,
AND BLUE.
THE MAIN DIFFERENCE BETWEEN A CAMERA AND THE EYE IS THAT THE FILM IN A CAMERA
PERMANENTLY STORES THE IMAGES FORMED ON IT, BUT THE IMAGES FORMED ON THE RETINA
DISAPPEAR WHEN YOU STOP LOOKING AT AN OBJECT.
A LASER IS A DEVICE THAT PRODUCES INTENSE LIGHT OF ONLY ONE COLOR AND WAVELENGTH.
LASER LIGHT IS DIFFERENT FROM NON-LASER LIGHT IN MANY WAYS. ONE IMPORTANT DIFFERENCE
IS THAT LASER LIGHT IS COHERENT.
WHEN LIGHT IS COHERENT, LIGHT WAVES MOVER TOGETHER AS THEY TRAVEL AWAY FROM THEIR
SOURCE