Refraction of Light

Matthayomsuksa 3

Refraction of Light

Matthayomsuksa 3

Vocabulary

refraction

ray of light

reflect

transparent

bend

dense

angle

Structure

IF Clause Type 1IF Clause Type 1

FormForm

if + Simple Present, will-Futureif + Simple Present, will-Future

ExampleExample

- If you shine a beam of light through the air, it will travel in a

straight line.- I will send her an invitation if I

find her address.- If I find her address, I will send her an invitation.

Refraction of LightIf you shine a beam of light through the air, it will

travel in a straight line. Rays of light usually travel in straight lines until they hit something. If a ray of light hits the surface of a sheet of glass, some light will be reflected by the surface of the glass. However, much of the light will pass through the glass, because glass is transparent. Water affects light rays in a similar way. Some light will be reflected off the surface of the water, but much of the light will pass through the transparent water. When a ray passes from air into glass the direction in which the light ray is travelling changes. The light ray appears to bend as it as it passes through the surface of the glass.

When a light ray passes from air into water a similar thing occurs: the light ray is bent as it strikes the surface of the water. This 'bending of a ray of light' when it passes from one substance into another substance is called refraction. The bending of a ray of light also occurs when the ray comes out of glass or water and passes into air.

What causes this bending?Glass and water are thicker and heavier than air.

They are said to be 'denser' than air. What happens is that light slows down when it passes from the less dense air into the denser glass or water. This slowing down of the ray of light also causes the ray of light to change direction. It is the change in the speed of the light that causes refraction. This is a bit like when a car goes partly off the road and some of the wheels go into the softer edge of the road. The softer surface drags on the wheels and slows them down. This can cause the car to pull to the left, slightly changing its direction.

Direction of bendingWhen a ray of light passes

from a less dense material (eg air) into a denser material (eg glass or water) it is bent away from the surface between the two materials. This means that in this situation the angle of refraction is always less than the angle of incidence. However, if the ray of light hits the surface at right angles (ie at 90°) to the surface, the ray is not bent.

When a ray of light passes from a denser material (eg water or glass) into a less dense material (eg air) it is bent towards the surface between the two materials. This means that in this situation the angle of refraction is always greater than the angle of incidence.

You can apply these rules for the refraction of light to any prism, triangular or rectangular. They also apply to light passing through lenses.

Activity 1

“Way of light”Activity 1

“Way of light”

EquipmentEquipment

Flash lightFlash light

PaperPaper

MirrorMirror

mirror

Point no. 1

Point no. 2

Point of flash light

Result

Point no. 1

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Point no. 2

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Lab Result“Way of light”

Activity 2

“Wonderful light”

Activity 2

“Wonderful light”

EquipmentEquipment

GlassGlass

Glass of waterEmpty glass

Equipment no.1 Equipment no.2

AA

GG

EE

BB

DDCC

FF

rulerruler

branchbranch

pencilpencil

stonestone

coincoin

leafleaf

shellshell

Lab Result“Wonderful light”

Equipment

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Experiment Process

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1.)……………………………………………………………………………….

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Result................................................................................................................................................................................................................................................................................................................................................................................................................................

Drawing

Drawing