Transcript Chapter 11-Sect. 3

Chapter 11-Sect. 3
Behavior of Waves
Reflection
• Reflection-occurs when a wave
strikes an object and bounces off
of it
• All waves (including sound, water
and light) can be reflected
– Ex: mirror reflections/echoes, etc.
Law of Reflection
• Incident beam—beam striking the
object
• Reflected beam—beam that bounces
off the object
• The line drawn perpendicular to the
surface of the object--NORMAL
(more on Law of
Reflection)
• According to the Law of
Reflection, the angle of incidence
is equal t the angle of reflection
• ALL REFLECTED WAVES OBEY
THIS LAW
Refraction
• Figure 14—pg. 340
• Pencil looks as if it is broken into two
pieces
• Refraction—the bending of a wave
caused by a change in its speed as it
moves from one medium to another
• Greater change in speed = greater bend of
waves
Refraction of Light in
Water
• Pg. 341-explains how the eye
perceives refraction
• Your vision assumes light rays
have traveled in a straight line,
whether in water or not
Diffraction
• When waves strike an object, they
can bounce off or be reflected
• If the object is transparent—
refraction
• Sometimes, waves are both
reflected and refracted
More on diffraction
• Diffraction—occurs when an object
causes a wave to change direction and
bend around it
• Diffraction and refraction both cause
waves to bend
• Refraction—waves pass through
• Diffraction—waves pass around
Diffraction and
Wavelength
• When an obstacle is smaller than
the wavelength, the waves bend
around it
• When the obstacle is larger than
the wavelength, the waves do not
diffract as much, or sometimes not
at all
Radio Waves
• Diffraction affects your radio’s reception
• AM radio waves have longer
wavelengths than FM radio waves
• AM radio waves diffract around
buildings, etc.
• FM waves do not diffract as much
• SO: AM radio reception is often better than FM
Interference
• When two or more waves overlap and
combine to form a new wave—
interference.
• Constructive—waves add together
• Destructive—waves subtract from
ea/other as they overlap
Standing Waves
• A special type of wave pattern that
forms when waves equal in
wavelength and amplitude, but
traveling in opposite directions,
continuously interfere w/ea other
• Nodes—where the two waves
always cancel
Resonance
• The ability of an object to vibrate
by absorbing energy at its natural
frequency--resonance