Transverse waves
The direction of vibration is perpendicular to the direction of propagation (water, light and seismic S-waves
Longitudinal waves
The direction of vibration is parallel to the direction of propagation (sound and seismic P-waves)
wave speed formula
v = f * wavelength
Refraction
The change in direction of a light ray passing from one medium to another
Refractive Index
The ratio of the speeds of a wave in 2 different regions
Critical angle
The angle of incidence at which the angle of refraction is 90 degrees and above which all light is totally internally reflected
human hearing range
20-2000Hz
human light range
700nm to 400nm (nanometer)
Factors of wave diffraction
1) wavelength of incoming wave
2) size of the gap
Properties of mirror images
1) Virtual
2) Laterally inverted
3) Same distance from mirror as object
4) Same size as object
virtual image
An image that cannot be projected on a screen
Refractive index formulas
With angles
n = sin i / sin r
with speed:
n = speed of light in vaccum / speed of light in medium
Total internal reflection definition
When a light ray hits the boundary b/w two materials of different densities, and is reflected rather than refracted
Total internal reflection conditions (2)
1) Angle of incidence must be greater than the critical angle
2) Light is passing from a more dense medium to a less dense medium
focal length
The distance from the centre of the lens to the principal focus
Dispersion
A prism splits a ray of white light into a spectrum of colour
Radio Waves (2)
1) Used in communication (radio & TV transmissions) and astrology
2) Long wavelength to travel long distance (radio waves diffract)
Microwaves (2)
Uses: Satellite communication, mobile phones and cooking (microwave)
Dangers: Internal tissue heating
Infrared waves (2)
Uses: thermal imaging, remote controllers (TV)
Dangers: Too much exposure to high energy infrared waves leads to skin getting burnt
Ultraviolet radiation (2)
Uses: Tanning beds, fluroscent lamps, security banking
Danger: High does can kill cells. Lower doses make cells potentially become cancerous
X rays (2)
Uses: medical and security scanners
Dangers: High doses can kill cells. Lower doses can cause cells to become cancerous and mutated
Visible light
Uses: Vision, photography
Gamma rays (2)
Uses: Medical imaging, sterilization, detection/treatment of cancer
Danger: Can kill the living cell/mutations
Conditions that determine diffraction (3)
1) If gap is smaller than wavelength –> reflection
2) If gap and wavelength are same size –> diffraction (circular waves)
3) If gap is larger than wavelength –> diffraction (slightly on the ends of waves)
