13. if + Simple Present, will-Future
if + Simple Present, will-Future
Example
Example
14. - 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
15. Refraction of Light
If 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.
16. 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.
17. 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.
18. Direction of bending
When 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.
19. 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.
23. Lab Result
“Way of light”
Point of flash Result
light
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Point no. 2 ………………………………………………………………………………………………………………
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