P13 Flashcards
What type of radiation is used to transmit a signal in an optical fibre?
Visible light
What is the critical angle?
The minimum angle at which total internal reflection takes place
Uses of total internal reflection
- fibre broadband
- doctors look at patients using endoscope
- decorations like Christmas tree lights
What are the two types of seismic waves?
P-waves and S-waves
Similarities and differences between P and S waves
P waves. S waves
longitudinal. transverse
faster. slower
solids n liquids. solids
What is a black body?
An object that absorbs all radiation falling on it, at all wavelengths, is called a black body.
What happens when an object is at a constant temperature?
This means that the object is absorbing radiation at the same rate at which it is emitting radiation.
What is a lens?
A lens is a transparent block that causes light to refract to form an image.
Why are microwaves used for satellite communication and not radio waves?
Microwaves pass straight through the atmosphere and are suitable for communicating with distant geostationary satellites, while radio waves are suitable for communicating with satellites in low orbit.
What properties make radio waves ideal for communication?
Radio waves are transmitted easily through air. They do not cause damage if absorbed by the human body, and they can be reflected to change their direction.
What type of seismic wave travels faster?
P waves travel much faster than S waves
What happens to S waves when they reach the boundaries of the Earth’s structure?
When S waves reach the boundaries of the Earth’s structure they both reflect and refract, causing them to travel in curved paths.
What type of wave has areas of rarefaction and compression?
Longitudinal
How does the wavelength of a wave affect its range?
Longer wavelengths travel further but carry less information; shorter wavelengths have shorter ranges but can carry more information.
What is a convex lens?
A convex lens is thicker in the middle than it is at the edges and converges light into one point called the focal point.
What is a concave lens?
A concave lens is thinner in the middle than it is at the edges. This causes parallel rays to diverge.
What happens to a wave if it crosses a boundary at an angle and slows down?
It bends towards the normal
What is the object called in which charges oscillate to create the radio waves?
A transmitter
What is an opaque object?
An object in which no light is transmitted
What type of object is the best possible emitter of radiation?
A perfect black body
What is the wave speed?
The speed at which energy is transferred through a medium
Wave period formula
period = 1/frequency
What does the size of refraction depend on?
How much the wave speeds up or slows down
Which type of electromagnetic wave is used when a traffic signal communicates with a car driver?
Visible light
Descirbe how radio waves are different from sound waves
- Radio waves are transverse
- Radio waves have a greater frequency
- Radio waves travel at the speed of light
- Radio waves can travel through a vacuum
Give the equation that links frequency, speed and wavelength of a wave
speed = frequency x wavelength
What is the unit for wavelength?
Metres
1 Megahertz = ? Hertz
1 Megahertz = 1,000,000 Hertz
What percentage of the energy that reaches Earth is reflected back into space?
29%
In what position do particles end up after a transverse wave has passed?
Same position
A student measures the distance from the peak of a water wave to the trough of a water wave. This distance is 0.80 m. State the amplitude of this water wave.
The amplitude will be half the distance from the peak to the trough. Therefore, the amplitude in this case would be 0.40 m.
What does not change when a wave crosses a boundary between two substances?
Frequency
4 things that happen to a wave at a boundary
- absorb
- reflect
- transmit
- refract
Why does the frequency of the wave not change at a boundary?
The frequency of the wave does not change because the source is producing the same number of oscillations (vibrations) per second.
What do we call sound waves that have been reflected of a wall?
Echo
What property of a body of water can be found using ultrasound?
Depth
What colour of visible light has the highest frequency?
Blue
What colour of visible light has the largest wavelength?
red
What properites of an image do concave lens always produce?
- Upright
- Diminished
- Virtual
Describe what happens in the electrical circuit when the car aerial absorbs radio waves
The radio waves are absorbed by a conductor, creating an alternating current. The information in the wave, is then decoded.
What is the angle of refraction?
The angle of refraction is the angle between the refracted light ray and the normal.
In the context of sound waves, what is a medium?
The substance that waves travel through
Heat radiation is transmitted via which form of wave?
Infrared
What distinguishes one colour from another?
The wavelength
Why is human hearing limited?
Human hearing is limited by the size and shape of our ear drums, as well as the structure of all the parts within the ear that vibrate.
What is meant by the wave period?
The wave period is the measure of time it takes for the wave cycle to complete
