P10 Waves Flashcards
Wave
Carries energy from one place to another without transferring matter
Amplitude
The height of a wave- a measure of how much energy it carries. It is measured in decibels. How loud something is
Longitudinal wave
A wave where particles vibrate in the same direction as the wave
Reflection
The waves bounce off a barrier (an echo with sound)
Refraction
When a wave changes direction upon entering or leaving a medium
Frequency
The number of waves passing a point in a unit time (measured in Hertz). The pitch of something
Wave equation
Velocity= frequency * wavelength
Vacuum
Empty space
Human range of hearing
A range of frequencies from 20 (or 40) - 20,000 Hz
Colour
Different wavelengths of light are interpreted by our brain as colour
Focal length
If light from infinity is converged by a converging lens the focal length is the distance from the centre of the lens to the principal focus.
Gamma radiation
The shortest wavelength (and highest energy) of light
Transverse wave examples
Light, water waves, P seismic waves (earthquakes)
Longitudinal wave examples
Sound, ultrasound, S seismic waves
Angle of incidence
The angle made by the ray of incidence (towards a boundary). It is equal to the angle of reflection
Angle of refelction
The angle made by the reflected ray, It is equal to the angle of incidence
Why do light rays refract/ change direction?
In a denser medium, light travels more slowly through it. Incident rays bend towards the normal
Refractive index
A measure of the degree to which light is slowed down by the glass block. The ratio (sin i / sin r)
Critical angle
The angle shown as C in diagrams. The angle right before it becomes totally internally refelcted
Total internal reflection
For all angles greater than the critical angle. All of the light will no longer be refracted out of the block, but will be reflected back into it.
Lens
Things that bend light and form images
Converging/ convex lens
A lens that is fatter in the middle than at the edges. The more curved it is, the more powerful/ converging it is
Principal focus
The point in which light rays arriving from infinity meet
Real image
An image than can be projected onto a screen
Virtual images
Images that cannot be picked up on a screen
Electromagnetic spectrum
Radio, microwaves, infrared, visible, ultra violet, x-ray, gamma rays (from long wavelengths to short)
Radio
The shortest wavelength. Used for TV communications and radio programs. No proven dangers
Microwaves
Used for cooking food, mobile phones and satellite TV Source: transmitters. Danger: if exposed for too long, you may develop cataracts in your eyes
Infrared
Not visible to human eye. Felt as heat. Dangers: possible burns/ eye problems. Used for intruder alarms, remote controls, TVs
X-rays
Used for medicine and security. Dangers: radiation exposure increases risks of getting cancer
What is sound caused by
Caused by the vibration of objects. This sets up a series of compressions (high pressure regions) and rarefactions (low pressure regions). This travels through a medium and our brain interprets the changes in pressure as sound
Gamma ray frequency
The highest. 10^19Hz
Radio frequency
The lowest. 10^8 Hz
Frequency range of electromagnetic spectrum
10^19 to 10^8 Hz
Transverse wave
A wave where the particles vibrate at 90 degrees to the direction of the wave
