Unit 3 Waves done Flashcards
What is a periodic phenomenon?
An event that happens regularly in a pattern every constant amount of time.
Eg: 12 months, weekly timetable, the moon appearance, Traffic light
What is Oscillation
Constant variation in magnitude or distance from a fixed point.
Ex: a ball tied to a rob not in contact with anything moving in a vacume
What is a wave and what is its Types?
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A wave is a disturbance in a medium that carries energy without a particle movement.
*Mechanical waves:
Waves that require a medium-like sound. They transmit energy by causing vibrations within particles.
Like sound
Forms:
Transverse Waves: Where particles vibrate at 90 degrees to the direction of the wave propagation.
Longitudinal Waves: Where particles vibrate in the same direction with the wave propagation. (انتشار)
Electromagnetic waves: Do not require a medium to spread. Like sunlight or any light from the electromagnetic spectrum
All electromagnetic waves are transverse waves
The 6 Wave characteristics
Frequency: The number of waves passing a fixed point in a unit of time.
Symbol: f Unit:Hz
Period: The time needed to complete 1 wave.
Wave length: The distance between 2 crest or throughs of a wave.
Crest: The highest part of a wave.
Through: The lowest part of a wave.
Amplitude: The maximum distance moved by particles in a wave from the central position.
Wave equation
Velocity= wavelength*frequency
V= λ*f
Electromagnetic spectrum different waves. How can they and sound waves be used medically.
All electromagnetic waves travel in the speed of light but their frequency is different.
Mnemonic: Raging Martians Invaded Venus Using X-ray Guns. (First letter of each)
1)Radio waves are used for radios and old televisions. Reflected in the ionosphere. Low risk high quality 3d images of the body organs
2)Microwave waves are used for microwaves and satellites communication. Can easily go through the atmosphere.
3) Infrared wave is heat and some animals can see it. Can measure the body temperature and areas with poor circulations.
4)Visible waves are what we see Roy G Biv.
5) Ultra violet waves can be sensed by most insects and are responsible for sunburns.
6) X Rays: Can show images of skeleton or soft tissues. Not for pregnant women.
7) Gamma Rays: Build up 3d images of internal organs and needs half life radioactive drug to be injected in the body.
Ultra sound is high frequency sound waves that takes low quality real times image of organs. Quick, safe and non expensive. ECO
Waves reflections
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When light or sound waves hit a smooth surface, like a mirror, they bounce off and change direction. This is called reflection. We use labels to understand this process:
easy, no worries
The normal line (N) is an imaginary line perpendicular (90 degrees) to the surface where the light hits.
The incident ray (I) is the incoming light ray that strikes the surface.
The angle of incidence is the angle between the incident ray and the normal line.
The reflected ray (R) is the light ray that bounces off the surface.
The angle of reflection is the angle between the reflected ray and the normal line.
According to the law of reflection, the angle of incidence equals the angle of reflection. This means that if you shine a light on a mirror at a certain angle, it will bounce off at the same angle, making the reflection predictable and easy to understand.
When light reflects off a smooth surface in a single direction it is called specular reflection. This is why you can see your reflection on shiny surfaces.
When light reflects off a rough surface, light is scattered in all directions. This is called diffuse reflection and is the reason
you can see your exercise book, but you can’t see your reflection in it.
Refraction
Refraction occurs when light, or any wave, bends as it passes from one medium to another, such as from air to water or from air to glass. This is because when light enters a new medium, its speed changes because the density of the medium affects how fast the light can travel. For example, light travels slower in water than in air.
no need for the exam:
snells law:
n1×sin(θ1) = n2 × sin(θ2)
n1 = incident index of refraction
n2 = refracted index of refraction
θ1 = incident angle
θ2 = refracted angle
air index of refraction: always 1.0
Sound waves and ultrasound waves
Sound waves a longitudinal waves caused by vibrations in matter. Sound waves can travel
through solid, liquid, or gas media, but not in a vacuum because there is no matter (no particles) to
vibrate.
We hear sound waves because the vibrations travel in the air into our ears, and cause the
eardrum to vibrate.
The human auditory range is
20 – 20 000 Hz. Sounds with a higher frequency than 20,000 Hz (20
kHz) are called ultrasound.
Ultrasound is useful for detection – finding things that you
can’t directly see.
e.g.
cracks in a solid block, or shoals of fish in the sea, or where
the bottom of the sea is. This works because ultrasound is
partially reflected when there is a change in the medium (some
ultrasound waves continue through). By detecting the
waves reflected – or echoed – back, you can work out how
far away the boundary between the two media is.
Diffraction
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A Phenomenon that occurs when waves encounter an obstacle or pass through an opening and bend around it, spreading out instead of traveling in a straight line.
