Waves, Light, Sound and
Transfer energy through
matter or space
May be longitudinal
Waves travel through a medium
bending of a
wave around the
edge of a barrier.
Reflection, refraction, diffraction
Need a medium to travel through
Speed of sound is 340 m/s in air
Water waves have transverse and longitudinal
Energy is transferred, but the particles stay essentially
in the same place
Light: particle or wave?
Light particles are called photons
Light: Particle or wave?
Light does not need a medium to travel
Change in frequency and pitch of a
Due to the motion of either the sound
source or the observer.
Doppler effect of sound
Doppler effect in light
As stars move away from earth,
there is a shift in the light towards
the red end of the spectrum.
• When light strikes a surface, it can
be transmitted, absorbed, or
Transmission of light
• When light is transmitted, a
substance is said to be transparent.
• The color that is transmitted is the
color that reaches your eye.
• Red glass absorbs all colors of light
except red, which it transmits.
Absorption of light
absorption of light
• Opaque objects reflect and absorb
• The color of an opaque object is the
color it reflects.
Opaque objects reflect
and absorb light
• This apple reflects red and
absorbs all other colors.
transmit some light
• Primary colors are red, green
• Primary colors may be combined
to make white light.
• 2 colors that combine to form white
Primary colors of light together form white light. But
primary pigments together make black.
This is because they absorb all colors.