learning materials and power point presentation for physical science quarter 2

1. LIGHT
WAVES

2. What is wave?
Waves are cause by disturbance or
vibrations creating motion that travels
energy through a medium from one
location to another location.

3. 3
3
A Medium is a material that can be a solid,
liquid or gas that transfer energy from one
place to another in a form of sound, light
and heat .
Mechanical Waves

4. 4
CLASSIFICATION
OF
WAVES

5. 5
Waves are classified according
to the:
1. Medium required or no medium
required
2. Direction of movement particles
of the medium relative to the
direction that the waves travel.

6. 6
Waves are classified according
to the:
1. Medium required or no medium required
 Mechanical Wave ( Medium
Required)
 Electromagnetic Wave ( No Medium
Required)

7. Mechanical waves is not capable to
transmit energy through a vacuum.
Mechanical waves are caused by a
disturbance or vibrations in medium whether
solid, liquid, gas and plasma. Mechanical can
produce longitudinal and transverse wave.
Mechanical Waves
Longitudinal Wave Transverse Wave

8. 8
8
Sound Waves
Ocean Waves
Tuning Fork
Ripples
Air, Solid, Liquid
Water
Solid and air
Water

9. Electromagnetic Wave
A wave that is capable to transmit energy
through vacuum and is capable of radiating energy
in the form of electromagnetic waves whichtravels
as fast as speed of light. Electromagnetic waves
produce transverse wave.

10. CLASSIFICATION OF WAVES

11. 11
11
Waves classified according to the
direction of movement particles
of the medium relative to the
direction that the waves travel.
 Longitudinal Wave
 Transverse Wave
CLASSIFICATION OF WAVES

12. 12
Longitudinal Waves
12
Lorem ipsum
conguetempus
In Longitudinal Wave particles of the medium
move in a direction( Back and Forth) parallel
to the direction of oscillations of waves and
motion of
energy
transport. CLASSIFICATION OF WAVES

14. 14
How to compute the number of
complete cycles in a longitudinal
wave?
CLASSIFICATION OF WAVES

15. 15
15
Transverse Wave
Transverse Waves are waves in
which the disturbance of the medium is
displace perpendicular ( right angle ) to
the direction of the wave to transport
energy.

16. 16

17. LIGHT WAVE
Light wave is a form of
electromagnetic wave that is propagated
perpendicular to the source of energy.
17

18. This kind of wave does not require
medium to travel as this type of wave is
traveling through space with speed of
3x108 m/s .
2

19. An example of this is sunlight,
it can reach earth even if the
outer space is basically a vacuum.
Another example of
Electromagnetic waves are radio
waves, gamma ray, microwave
etc.

20. PROPERTIES
OF
LIGHT 20

21. 21
A. Reflection – as light travels through matter, it
might encounter smooth or rough surface. If the
surface is perfectly smooth, light rays undergo
reflection. a mirror is a good example of a very
smoot surface that reflects light. If the surface is
rough, light is reflected in many direction.
SMOOTH SURFACE ROUGH SURFACE

22. 22
B. Refraction - This is also known as bending.
There is the change in direction of light wave
as light passes from one medium to another.
Light bends when it changes medium because
the speed of
light varies in
each medium.

23. 23
When light moves from a material in which its
speed is high to a low, like air to glass, then
the ray is bent toward normal.
If light moves from a material in
which the speed is low to one in
which the speed is higher, then
the ray is bent away from
normal.

24. Arrow Changing Direction!
Materials Needed:
• Piece of Paper
• Marker
• Glass
• Water

25. “
Step 1 – Get a sheet of paper and draw two
arrows on it. One arrow near the top and one
arrow near the bottom. Make the arrows point
in the same direction.
Step 2 – Fill a glass with water.
Step 3 – Slowly lower the piece of paper
behind the glass of water. Observe. 25

26. Broken Pencil Illusion
Materials Needed:
•Clear, round drinking glass
•Pencil
•Tap water

27. Steps
1.Fill the drinking glass about two
thirds of the way with water.
2.Place the pencil inside the glass on
an angle, so it’s resting on the rim.

28. C. Transmission - materials allows light that
falls on them to move through the material
without being reflected.
Transparent- Materials that allow
transmission of light through them.
Examples: Glass and clear water
Opaque- materials that do not allow any
transmission of light.

30. D. Absorption - Ability of objects to absorb
light, this occurs when an object does not reflect
or transmit the light. When you touch the object
that absorbs light energy, the object feels warm.
Generally, black
objects absorb all
light and white
objects absorb
no light.

31. Newton and
Descartes
Concept of
Light

32. 32
White light is made up of all the visible
colors in the electromagnetic spectrum. This
fact can be proven once light enters prism.

33. 33
Refraction of light is affected by the
light's wavelength. Violet has the highest
frequency and is refracted the most. Red
has the lowest frequency and is
refracted
the least.

34.  In the seventeenth century, most
people believed colored light was a
form of shadow made by mixing white
light with darkness.
Descartes thought color was caused by the
spinning motion of particles that made up
light.

35. But in 1665, Isaac Newton study about light
and colors. He darken the room and create a
hole in the window shutter. This allows a
beam of sunlight to enter the room. Then he
obtained a glass prism and placed it in the
Sunbeam. The result was a spectacular
multicolored band of light that to a rainbow.

37. 37
To further prove that colors came from the sunlight
and not from the prism he put a card with a hole in
it between two prisms, allowing only red light from
the first prism to go through the second prism. The
red light going through the second prism did not
split into different colors, or turn white again; it
remained red. Newton repeated the same
experiment with all of the colors and got the same
result.

39. 39
Newton was able to prove that prism
retracts white light resolving it into its
component colors namely red, orange,
yellow, green, blue and violet. These
colors are usually, found in the
rainbow.

40. 40
Dual Property of Light
As wave
As particle

41. 41
Light As A Wave
 It has the ability to diffract or bend around an
object.
Diffraction involves a change in direction of waves
when they pass from an opening or around obstacles
along their path.
Refraction happens when light waves change
direction as they travel through materials of different
refractive indices, say water and air.

42. 42
Light As Particles
The photo-electric effect is also evidence that light behaves
as particles. When light with enough energy falls or hits a
metal, electrons are dislodged or knocked off from it to
produce a positive (+) metal surface. The amount of light
energy (known as
photon)contains a fixed
amount of energy or
quantum that depends on
the frequency of the light.

43. Atomic Spectra

44. As long as electron stays in the orbit, it does not
absorb or emit energy and said to be in its ground
state.
44

45. When the atom absorbs energy, its electrons
become excited and occupy a higher energy level. At
this point the electron is in its excited state.
45

46. As electrons leave the excited state and return to its
ground state again, they emit energy in the form of
photon.
46

47. The set of frequencies of electromagnetic spectrum
emitted by excited atom is referred to as the atomic
emission spectra. Every element emits a specific
energy and wavelength producing a unique set of
banding pattern serve as fingerprints of every
element.

48. 48
Relationship of
Frequency and
Energy

49. 49
Frequency is the number of cycle in a
wave. The higher the energy the higher
the number of cycle. Lowering energy also
decreases the number of complete cycle
in a wave.

50. Practical
Application of
Photon Theory

51. 51
A. Why is red light commonly used in dark
room?
Red light is the region of the visible light with
the longest wavelength (620-780 nm) and with
lowest frequency; hence has the lowest
energy. Because of its low energy, red light is
considered as “safe light” and ideally used in
photographic dark rooms.

52. 52
B. Why do people get easily sunburned by
ultraviolet (UV) light but not by visible light?
Ultraviolet (UV) light has shorter wavelength and
higher frequency and shorter wavelength than
visible light this means that it has high energy.
Therefore, exposure to UV light can cause sunburn
or even skin cancer (prolonged exposure) faster
than exposure to visible light .

53. C. How do human eyes perceive colors?
The human eye can perceive colors because of its cones
cells. There are three different cone cells present in the
retina of our eyes, each contains photosensitive pigment
to certain wavelength.
The L cone is photosensitive to red (long wavelength).
The M cone is photosensitive to green (middle
wavelength).
The S cone is photosensitive to blue (short wavelength).

54. 54
Suppose a 550 nm wavelength of light enters
your eye, what color of the light will you
perceive?
The light with 550 nm
wavelength will
stimulate the green
receptor more
strongly than the red
receptor and
therefore, your eyes
will perceive green
light.

55. When a light with a 580 nm wavelength
enters your eyes?

56. Both the red and green receptors will be
strongly stimulated hence your eyes will
perceive yellow color based on the additive
color mixing.

57. “
57

58. THANK
YOU! 58