Chapter 15- Transmission And Reflection Of Waves Flashcards
Method of energy transfer activity
Using trolleys connected with springs
Energy pulse to one is transferred to all
Speed of sound in air (at 20*)
340 m/s
Experiment to find speed of sound in air
Using two beam oscilloscope
And a signal generator
Microphone will pick up sounds from speaker and these oscillations will compare to the ones from the speaker itself
Phase difference combined with physical distance will show speed of sound
Transverse waves model uses
Model of masses connected by springs and the resolution of forces
The pulse moves along the masses with a speed dependent on …
Magnitude of the masses
Tension in the springs
Speed of transverse wave eq
C= square root (tension in wire/mass per unit length)
Electromagnetic waves through a vacuum speed
3x10^8 m/s
Intensity eq
Intensity = power/ area
When a wave is incident on an interface between two different media, the energy may be
Absorbed
Transmitted
Or reflected
Law of reflection def
States that the angle between the INCIDENT ray and the NORMAL drawn at the point of REFLECTION
Is equal to
The angle between the REFLECTED EA and the NORMAL in the plane of reflection
Wavefront
Line or surface in a wave along which all the points are in phase
Refraction is caused by
Change in wave speed between two media
When speed is increased
Path of waves is directed away from the NORMAL
When the wave speed is decreased
The path of the waves is deviated towards the NORMAL
In shallow water wave speed is
Slower than in deep water
In deep water wave speed is
Faster than in shallow water
In a denser medium
Light travels more slowly
In a less dense medium
Light travels faster
Light and glass
Which is more dense?
Light is
Refractive index eq
Refractive index from medium 1 to medium 2 =
Speed in medium 1/ speed in medium 2
What is Snell’s law
States that the refractive index for a wave travelling from one medium to another is given by the expression
Sin[]1/ sin[]2 = v1/ v2 = 1n2
N1 Sin[]1= N2 Sin[]2
Does refraction occur for all waves?
YES
Critical angle def
Angle above which total internal reflection occurs
Snells law simple
N1/n2 = sin[]2 / sin[]1
Critical angle eq
Sin C= n2/ n1
Converging lens shape
()
Diverging lens shape
)(
Focal point def
Point of a lens is the point where parallel rays of light will meet, or appear to diverge from, after passing through the lens
Converging lens form a
Real focus
Diverging lens form a
Virtual focus
Focal length
Distance between optical centre of the lens and the focal point
Power of a lens relates to
The ability of the lens to deviate rays of light through large angles
The more powerful a lens
The shorter the focal length
Power of lens eq
1/ focal length (m)
Power of lens unit
Dioptre
M^-1
Total power calculated by
The sum of all the lenses
Types of image created (2)
Virtual
Real
Principle axis
A line that passes normally through the optical centre of the lens
Optical centre
The centre of a lens is the point through which rays of light will pass without deviation
The lens equation
1/u + 1/v = 1/f
All distances given positive values if real images formed
Converging = positive value focal length Diverging = negative value focal length
Key words to describe reflected images
Enlarged, smaller
Real, virtual
Inverted, erect
Plane polarised waves def
Are transverse waves in which the oscillations occur in a single plane
Polarised waves can only work for oscillations in
One direction
Horizontal or vertical
Polarising filter
Filters waves in certain oscillation decoration
Longitudinal waves cannot be polarised because
The waves have particles that have no components of oscillations in the planes perpendicular to the direction
How to polarise microwaves using transmitter
Turn receiver 90* rotation to polarise microwaves or radio waves
How is a light polarisation filter made
Made from polymers
With the molecular chains aligned in one direction
Stress analysis how
Put load-bearing components under stress
View through crossed sheets of Polaroid
Multicoloured interference stress patterns analysed to detect potential regions of weakness
A scans abbreviated from
Amplitude scans
B scans abbreviated from
Brightness scans
Pulse- echo techniques
Used to calculate speed of sound
And then to help medicine and scans for things
As well as in underwater exploration
What to remember about distance with pulse echo techniques
The distance is doubled in the experience
Type of electromagnetic wave used in pulse echo techniques
Ultrasound
Amplitude scans used to
Determine depth of boundaries between tissues or bone and tissue
Coupling gel needed so very little is reflected from the skin
Brightness scans used to
Detect position of reflecting boundary
They give a display/ image
