LIGHT
Grade 7 - Unit 6
Application of refraction of light
REFLECTION
OF LIGHT
When a ray of light approaches a
smooth polished surface and the
light ray bounces back, it is called
the reflection of light.
Why don’t we see reflection on all the
surfaces?
LAWS OF REFLECTION
Link https://www.youtube.com/watch?v=ETF2-Zz3J18
Textbook Questions Pg 193
REFRACTION
Refraction is the change in
the direction of a wave
passing from one medium to
another.
SPEED OF LIGHT IN DIFFERENT MEDIUM
Textbook Questions pg 200
Application of refraction of light
RAINBOW
Rainbows are the result of the refraction
and reflection of light. Both refraction and
reflection are phenomena that involve a
change in a wave's direction. A refracted
wave may appear "bent", while a reflected
wave might seem to "bounce back" from a
surface or other wavefront
NEWTON’S
DISCOVERY
Newton began his
investigations by cutting a
pinhole in his window shade
to let in sunlight, which
showed up on his wall as a
round illuminated area.
Refracted by a prism, it
turned into an oblong area
with a rainbow of colors.
SPECTRUM
The band of coloured components of
a light beam is called its spectrum.
DISPERSION
Process of white light splitting into its constituent colours is
termed as dispersion.
FORMATION OF
RAINBOW
Rainbows are formed
when sunlight is
scattered from raindrops
into the eyes of an
observer. Most raindrops
are spherical rather than
the often depicted
'teardrop' shape and it is
this spherical shape that
provides the conditions
for a rainbow to be seen.
Refraction
Reflection
Textbook questions pg 202
Refraction
COLORS OF LIGHT
Formation of white light does not
always need 7 color spectrum.
White light can also be created by
mixing only three distinct light
frequencies, given that they are
broadly separated on the visible light
spectrum.
The most common set of primary
colours is red (R), Green (G) and blue
(B)
R+B+G = W
ADDING COLORS
SUBTRACTING COLORS
Textbook
Questions pg 214
THE MILKY WAY
The Milky Way is the galaxy that
includes our Solar System, with the
name describing the galaxy's
appearance from Earth: a hazy band
of light seen in the night sky formed
from stars that cannot be individually
distinguished by the naked eye.
SHAPES OF THE GALAXIES
The smallest of galaxies contain a “mere”
few hundred million stars while the largest
galaxies contain up to one hundred trillion
stars!
Scientists have been able to segment
galaxies into 4 main types:
1. spiral,
2. elliptical,
3. and irregular.
Irregular
Spiral
Elliptical
1. Our galaxy is spiral galaxy
2. The closest known galaxy to the milky way is
“canis major dwarf galaxy”
a. Shape - elliptical
b. Distance 240 000 million million km away
What are galaxies made of ?
Galaxies are made of
1. Stellar dust - dust found in space
2. Gas
3. Stars
4. Solar systems held together by gravity
● Nearly all large galaxies are thought to also
contain supermassive black holes at their centers.
Asteroid
Asteroids are small, rocky objects that orbit the Sun.
Although asteroids orbit the Sun like planets, they are
much smaller than planets.
● Asteroid size ranges from 975 km to 2m
● They are irregular in shape
● Most of the asteroids are between the orbits of Mars
and Jupiter which is called as the asteroid belt
CERES
● Largest and first
asteroid discovered
● Diameter 975 km
● Covered with craters
● Has a core, mantle and
crust
ITOKAWA
● Smallest asteroid visited by
spacecraft
● 530 m long 250m wide
● Appears to be made from
lumps of rock (made from
other planets or moon
● Tidal forces from other
planets can change its shape
Asteroid impact on Earth
Many asteroids
break up on the
Earth’s
atmosphere
and never
reach the
surface
Reasons why Asteroid impact Earth
1. The Earth exerts a strong force
of Gravity on passing objects
such as asteroid
2. Many asteroids have orbits that
pass relatively close to Earth
Link - https://www.youtube.com/watch?v=dvd47rMYia0
Textbook questions
THANK YOU