Waves Flashcards
What is a wave
A wave transfers energy without any permanent transfer of matter
What are the two types of wave
Longitudinal and transverse
What are transverse waves and give examples
Waves were the direction of oscillation is perpendicular to the direction the wave travels
e.g. Light and water
What are longitudinal waves and give examples
Waves where the direction of oscillation is the same as the wave direction
e.g. sound waves and ultrasound
What is frequency
The number of waves made per second measured in Hertz
What is wavelength
Crest to crest (one complete wavelength) measured in meters
What is time period
time for one wave to pass (seconds)
what is amplitude
Maximum height of crest or depth of trough (a)
Give the equation relating velocity frequency and wavelength
Velocity = frequency x wavelength
Give the equation relation frequency and time
Frequency = 1/time period
Time period = 1/frequency
What happens when waves go from, deep water to shallow water
Frequency doesn’t change
Velocity decreases
So wavelength decreases
(if waves hits the boundary at an angle the direction changes )
What happen to waves when they go from shallow water to deep water
Frequency doesn’t change
Velocity increase
So wavelength increases
(if waves hits the boundary at an angle the direction changes )
What happens to the waves and sound when the source is moving away from you
This is the Doppler effect
- Wavelength will increase
- Frequency will decrease
- The pitch will be lower
What happens to the waves and sound when the source is moving towards you
- Wavelength will decrease
- Frequency will increase
- Higher pitch h
How does speed affect the doppler Effect
The faster movement the bigger the change
What is the ray going towards the plane mirror called
Incident ray
What is the ray going away from the plane mirror called
Reflected ray
What are the laws of reflection
- Angle of incidence = angle of reflection
- incident ray, reflected ray and normal all lie on the same plane
What are the properties of an image in a plane mirror
- As far being the mirror as the object is in front
- The same size as the object
- Laterally inverted
- Upright
- Virtual (It cannot be caught/projected on a screen)
When does refraction occur
Refraction occurs when light passes from one medium to another causing a change in speed and direction
- When light slows down it refracts toward the normal e.g air to glass
- When light speeds up it refracts away from the normal e.g. glass to air
What is the equation for the refractive index
n = sin i / sin r
What is the critical angle of glass
42
What is total internal reflection
When the light ray goes from a more dense medium into a less dense medium and the angle of incidence is greater then the critical angle
What is a critical angle
The angle of incidence in the denser medium that gives an angle of refraction of 90 degrees in the less dense medium
In a longitudinal wave give 2 features
Compressions (close together)
Rarefaction (spaced out)
What is the equation of the critical angle
n = 1/sin c
sin c = 1/n
n is the refractive index
c is the critical angle
Why does water never look as deep as it real is
- Light rays reflected from the objects surface refract away from the normal at the waters surface
- From above the person sees a virtual image of the object which appears which appears higher up
What causes sound
vibrations
What does frequency affect in sound waves
pitch
what does amplitude affect in sound waves
loudness
What is the human amplitude range
20 Hz - 20,000 Hz
What is the method to find the speed of sound
- Stand a long distance from large flat wall
- Measure distance with a trundle wheel
- Make loud sound using starting pistol
- Start stopwatch when “bang” is heard
- Stop when echo is heard
- Repeat timing, ignore anomalous results, find average
- Speed = distance / time
Give the electromagnetic spectrum in order
Radio wave, microwave, infrared radiation, visible light, ultraviolet, x-rays, gamma ray
Give the uses of radio waves
broadcasting and communications
Give the uses and dangers of microwaves
Uses: cooking and satellite transmissions
Dangers: internal heating of body tissue
Give the uses and dangers of infrared radiation
Uses: heaters and night vision equipment
Dangers: skin burns
Give the uses and dangers of ultraviolet
Uses: fluorescent lamps
Dangers: damage to surface cells and blindness
Give the uses of visible light
Optical fibres and photography
Give the uses of x rays
observing the internal structure of objects and humans
Give the uses and dangers of gamma rays
Uses: sterilising food and medical equipment
Dangers: cell mutation and cancer
What are 4 properties of electromagnetic waves
- They transfer energy
- They are all transverse waves
- They all travel at the same speed in a vacuum
(3.0 x 10 to the power of 8) - They all can be reflected and refracted
How is the electromagnetic spectrum ordered
wavelength
(radio waves longest and gamma shortest)
How do optic fibres work
The edge of the fibre is always higher then the critical angle so the light is always totally internally reflected
