Waves Flashcards
Wave motion
Transfer of energy from one place to another
Frequency (f)
Number of cycle or waves in one second, unit hertz (Hz)
Wavelength (λ)
Length of one complete wave, unit, meters (m)
Amplitude (a)
Maximum displacement of medium from its mean position, meters
Wavefront
Line where the disturbance of all particles are at the same point from the central position
eg. a crest of a wave is a wavefront
Wave equation (x2)
v = f x λ
v is the speed of wave in m/s
f is the frequency in (hertz) Hz
λ is the wavelength in meters
f = 1 / T
T is the time period of the wave in seconds
Movement of particles (in 2 different waves)
Longitudinal waves=> back and forth parallel to the direction of the waves (oscillate along the same direction as the energy transfer/ direction of wave)
Transverse waves=> perpendicular to the direction of the waves (up and down)
Law of reflection
Angle of incidence (i) = angle of reflection
angle iº = angle rº
Refraction in relation to mediums and normal line
From lighter to denser medium → light bend towards the normal
From denser to lighter medium → light bend away from the normal
Refractive index (n)
n = sin iº in air or vacuum / sin rº in material
n = speed of light in air or vacuum / speed of light in material
Diffraction
Bending of waves around the edges of a hard surface
Dispersion
Separation of different waves according to colours or frequency for example by using a prism
Image from a plane mirrors
Virtual, upright, same size and laterally inverted and same distance from the mirror inside
Image from a convex lens
When close: virtual, enlarge, upright
When far: real, small, upside down
think about it like a magnifying glass
Image from a concave lens
Virtual, upright, small
Critical angle
When light goes from denser to lighter medium, the incident angle at which the reflected angle is 90º, is called the critical angle.
Total internal reflection (TIR)
When light goes from denser to lighter medium, the refracted ray bend inside the same medium called (TIR) eg optical fibre
Electromagnetic Spectrum: travel in vacuum, oscillating electric and magnetic fields
←λ (decrease) and f (increase)
λ (increases) and f (decrease)→
←λ (decrease) and f (increase)
λ (increases) and f (decrease)→
Gammas rays X-Rays Ultra violet rays Visible (light) rays Infrared rays Micro waves Radio waves
Rays and their uses
Gamma rays: for killing cancer cells
X-rays: in medicine
UV rays: for sun tan and sterilisation of medical instruments
Visible light: light rays, monochromatic means one colour
Infrared: remote controls, treatment of muscular pain
Micro waves: international communication, mobile phones
Radio waves: radio and television communication
Colours of visible light VIBGYOR wavelengths
Violet 4×10^-7m, Indigo, Blue, Green, Yellow, Orange, Red 7×10^-7m
Speed of light waves or electromagnetic waves
In air:
3×10^8 m/s
In water:
2.25×10^8 m/s
In glass:
2×10^8 m/s
Light wave
Transverse electromagnetic waves
Sound wave are longitudinal waves
particles of the medium come close to each other → compression
particles of the medium move away → rarefaction
Echo
v = 2 x d / t
v is the speed of sound waves
d is the distance in meters between source and the
reflection surface
t is the time for echo
Properties of sound waves in relation to the shape of the wave
Pitch is similar to the frequency of the wave
Loudness is similar to the amplitude of the wave
Speed of sound waves
Air:
330-340 m/s
Water:
1400 m/s
Concrete:
5000 m/s
Steel:
6000–7000 m/s
Diffraction rules
Greater frequency means greater diffraction and more wave cycles
Greater gap less diffraction
Greater wavelength greater diffraction
