3 Waves Flashcards
Waves transfer energy …
without a transfer of matter
Transverse
Travsverse waves have vibrations that are …
parallel to the direction of the wave
Give 3 examples of:
Transverse waves
Light - EM Spectrum
Water
Secondary seismic waves
Longitudinal
Longitudinal waves have oscillations that are…
parallel to the direction of the wave
Give 2 examples of:
Longitudinal waves
Sound
Primary seismic waves
Define:
Amplitude
The maximum displacement of any particle/wave from its undisturbed position (equilibrium)
WAVES
difference between longitudinal and transverse waves
transverse = wave that vibrates perpendicular to the direction of the oscillation
e.g. light (EM Spectrum)
longitudinal = wave that vibrates parallel to the direction of the oscillation
e.g. sound
define wavefront
2 or more waves moving together have wavefronts, imaginary planes connect points on adjacent waves, vibrate together
define amplitude
maximum displacement of particles from their equilibrium position.
define wavelength
distance between a particular point on one cycle of the wave and the same point on the next cycle.
define frequency
number of waves passing a particular point per second. Is measured in Hertz (Hz).
define time period
time it takes for one complete wave to pass a particular point
waves transfer energy and information without transferring _______
matter
wavespeed =
wavelength x frequency
v = lamda x f
m/s = Hz x m
frequency =
1/time period
Explain the doppler Effect
When a car is not moving and its horn sounds, the sound waves we receive are a series of evenly spaced wavefronts.
If a car is moving, wavefronts of the sound are no longer evenly spaced.
Ahead of the car wavefronts are compressed as the car is moving in the same direction as the wavefronts. This creates a shorter wavelength and a higher frequency.
Behind the car wavefronts are more spread out as the car is moving away from the previous wavefronts. This creates a longer wavelength and a lower frequency.
features of a transverse wave
properties of EM waves
Transfer energy
Are transverse waves
Travel at the speed of light in a vacuum
Can be reflected and refracted
features of a longitudinal wave
rarefactions and compressions
particles vibrate back and forth
all EM waves travel at same speed in _____ ______
free space
order of em waves from lowest to highest frequency
Radio Waves
Microwaves
Infrared (IR)
Visible Light
Ultraviolet (UV)
X – Rays
Gamma Rays
which has the shortest wavelength and has the lowest frequency
radio waves
which colour has the shortest wavelength and lowest frequency in the visible light spectrum
red
Uses of EM waves:
Radio Waves
Microwaves
Infrared (IR)
Visible Light
Ultraviolet (UV)
X – Rays
Gamma Rays
- radio waves: broadcasting and communications
- microwaves: cooking and satellite transmissions
- infrared: heaters and night vision equipment
- visible light: optical fibres and photography
- ultraviolet: fluorescent lamps
- x-rays: observing the internal structure of objects and materials, including for medical applications
- gamma rays: sterilising food and medical equipment.
risks of exposure to EM waves:
microwaves
infrared
ultraviolet
gamma rays
- microwaves: internal heating of body tissue
- infrared: skin burns
- ultraviolet: damage to surface cells and blindness
- gamma rays: leads to ionisation of cells causing mutation which might produce cancerous cells
How to reduce risks of:
UV
gamma
UV = stay in shade, sunglasses, sun cream
Gamma = led clothing, leave room - reduced exposure
practical: investigate the refraction of light, using rectangular blocks, semi-circular blocks and triangular prisms
- Set up your apparatus as shown in the diagram using a rectangular block.
- Shine the light ray through the glass block
- Use crosses to mark the path of the ray.
- Join up crosses with a ruler
- Draw on a normal where the ray enters the glass block
- Measure the angle of incidence and the angle of refraction and add these to your results table
- Comment on how the speed of the light has changed as the light moves between the mediums.
- Repeat this for different angles of incidence and different glass prisms.
refractive index =
n =
sin (angle of incidence) / sin (angle of refraction)
sin (i) / sin(r)
practical: investigate the refractive index of glass, using a glass block
- Set up your apparatus as shown in the diagram using a rectangular block.
- Shine the light ray through the glass block
- Use crosses to mark the path of the ray.
- Join up crosses with a ruler
- Draw on a normal where the ray enters the glass block
- Measure the angle of incidence and the angle of refraction and add these to your results table
- Calculate the refractive
index - Repeat steps 2 – 7 using
a different angle of
incidence - Find an average of your
results.
practical: investigate the refractive index of glass, using a glass block
- Set up your apparatus as shown in the diagram using a rectangular block.
- Shine the light ray through the glass block
- Use crosses to mark the path of the ray.
- Join up crosses with a ruler
- Draw on a normal where the ray enters the glass block
- Measure the angle of incidence and the angle of refraction and add these to your results table
- Calculate the refractive
index - Repeat steps 2 – 7 using
a different angle of
incidence - Find an average of your
results.
describe the role of total internal reflection in transmitting information along optical fibres and in prisms
optical fibres - use light to carry digital information over long distances
explain what is the critical angle and the 3 conditions
The angle of incidence which produces an angle of refraction of 90 (refracted ray is along the boundary of the surface).
When the angle of incidence is greater than the critical angle, total internal reflection occurs (all light is reflected at the boundary).
This effect only occurs at a boundary from a high refractive index material to a low refractive index material.
When the angle of incidence is lesser than the critical angle, light partially internally reflected
when the angle of incidence is equal to critical angle, lots of internal reflection and emerging ray along surface
critical angle =
c =
sin ^-1 (1/n)
refractive index =
n =
1 / sin(c)
sound waves are longitudinal waves and light is transverse waves and both can be ______ and ______
reflected and refracted
frequency range for human hearing
20–20 000 Hz
explain journey of light ray from air into glass at angle and vice versa
Glass is denser than air, so a light ray passing from air into glass slows down. If the ray meets the boundary at an angle to the normal, it bends towards the normal.
A light ray speeds up as it passes from glass into air, and bends away from the normal by the same angle.
the denser the material, the ________ that light travels
slower (bends closer to normal)
