REFRACTION TRANSPARENT SUBSTANCES REFRACT LIGHT ITS NOT MAGIC

REFRACTION TRANSPARENT SUBSTANCES REFRACT LIGHT

IT’S NOT MAGIC… IT’S SCIENCE!

HOW LIGHT REFRACTS • REFRACTION IS DUE TO CHANGES IN THE SPEED OF LIGHT. • IN SPACE, LIGHT TRAVELS AT 300 000 KM/S. SPACE IS A VACUUM, AND THERE ARE NO PARTICLES TO GET IN THE WAY OF LIGHT AND SLOW IT DOWN. • IT IS IMPOSSIBLE TO MOVE AT TOP SPEED WHEN PARTICLES GET IN THE WAY. (THINK OF WHAT IT IS LIKE TO MOVE THROUGH THE HALLWAY IN BETWEEN BELLS!) • IF THE LIGHT STRIKES A MEDIUM OF DIFFERENT DENSITY AT AN ANGLE, IT REFRACTS (OR BENDS!)

REFRACTION IN DIFFERENT MEDIA • MEDIA OR A MEDIUM MEANS A DIFFERENT SUBSTANCE • THE DENSER THE NEW MEDIUM, THE MORE THE LIGHT SLOWS DOWN. THE SLOWER THE LIGHT TRAVELS, THE MORE IT WILL BEND OR REFRACT!

ACTIVITY • GROUPS OF TWO “POP QUIZ” • (CHECK AND REFLECT QUESTIONS PAGE 203)

LENSES REFRACT LIGHT

LENSES • A LENS IS A PIECE OF CURVED GLASS OR OTHER TRANSPARENT MATERIAL (SOMETIMES PLASTIC) • IT IS SMOOTH AND REGULARLY SHAPED SO WHEN LIGHT STRIKES IT, IT REFRACTS IN A PREDICTABLE WAY.

CONCAVE LENS • A CONCAVE LENS IS THINNER IN THE CENTRE THAN AT THE EDGES • AS PARALLEL RAYS PASS THROUGH, THEY ARE REFRACTED AWAY FROM THE CENTRE OF THE LENS. • THE RAYS DIVERGE.

CONVEX LENS • A CONVEX LENS CURVES OUTWARD AND IS THICKER IN THE MIDDLE THAN AT THE EDGES. • AS PARALLEL LIGHT RAYS TRAVEL THROUGH, THEY MOVE TOWARD EACH OTHER. • THE RAYS CONVERGE.

CONVEX LENSES • THE ABILITY TO BRING LIGHT RAYS TOGETHER IS USEFUL BECAUSE: • IT CAN ACT AS A LIGHT COLLECTOR (MUCH LIKE A CONCAVE MIRROR). THIS TYPE OF LENS IS USED IN A REFRACTING TELESCOPE. • THE LIGHT RAYS ACTUALLY MEET AT A POINT AND FORM A REAL IMAGE - THE IMAGE CAN BE PROJECTED INTO A SCREEN. HOWEVER, IT IS UPSIDE DOWN!

CONVEX LENS • REAL IMAGE • THE IMAGE APPEARS UPRIGHT AND BIGGER, AND FORMS ON THE SAME SIDE AS THE OBJECT FOR EXAMPLE: A MAGNIFYING GLASS

ACTIVITY • DIVIDE A PIECE OF BLANK PAPER INTO FOUR RECTANGLES. • DRAW AND LABEL FOUR DIAGRAMS SHOWING THE RAYS BEHAVE WHEN THEY INTERACT WITH EACH MIRROR AND LENS. Concave Mirror Convex Mirror Concave Lens Convex Lens HOW

ACTIVITY • DIVIDE A PIECE OF BLANK PAPER INTO FOUR RECTANGLES. • DRAW AND LABEL FOUR DIAGRAMS SHOWING THE RAYS BEHAVE WHEN THEY INTERACT WITH EACH MIRROR AND LENS. Concave Mirror Convex Mirror Concave Lens Convex Lens HOW