Waves Flashcards
Define wave
Transfer of energy without transfer of matter
Define longitude wave
Direction of vibration is parallel to the direction of wave travel
Define Transverse wave
Direction of vibration is perpendicular to the direction of wave travel
List the 6 features of a wave
1) Wavefront
2) Wavelength
3) Frequency
4) Crest
5) Trough
6) Amplitude
7) Wavespeed
Describe wavelength
The distance between 2 successive trough (In meters)
Describe amplitude
Maximum displacement from the equilibrium point (meters)
Describe frequency
number complete waves generated per one second (S^-1 or Hertz)
Describe period
Time for 1 complete wave to be generated (Seconds)
Describe wavefront [2]
1) A line drawn to connect all points that are in phase in a wave
2) Crest of the wave
Describe the crest
The part of a wave with the most magnitude; the highest part of a wave
Describe the trough
The part of a wave with the least magnitude; the lowest part of a wave
Wave speed (V)
= Frequency (f) x Wavelength (λ)
Law of reflection
Incident angle = relfected angle
All waves will [3]
1) Reflect
2) Refract
3) diffract
Define wave refraction
1) Changes the direction of wave in different medium due to the change in its speed
2)When a wave slows down it bends towards the normal (Vice versa)
3) Slows down when traveling through mediums of higher refractive index
Define wave diffraction
The spreading of waves when going through a narrow opening
When is the diffraction wave most pronounced?
Size of opening is approx equal to the wavelength
Refraction of light to more dense material
Ray bends towards normal
Refraction of light to less dense material
Ray bends away from normal
Define critical angle
1) As incidence angle increase, refracted angle increases too
2) When the refracted angle becomes 90 degree the incident angle is critical angle, c
Define internal reflection
1) When light travels from a denser medium to a less dense medium, the refracted angle is larger than the incident angle (r > i)
2) some light is internally reflected
Refractive index formula fo r angles
n= sin i/ sin r
Describe an optic fibre
Thin fibre of glass or clear plastic that can carry light from one end to another
3 advantages of using optic fibre for telecommunication
1) Transmission of large amounts of information over great distances
2) Light doesn’t leak out of the fibre so it can travel longer before signal is weak
3) It cannot be tapped (Listened on by others)
What happens to light as it travels through a prism?
1) White light may be separated into all its colours by passing it through a prism
2) refraction
3) Violet light is refracted the most, whilst red light is refracted the least
This splits up the colours to form a spectrum
How does red and violet corresponds to different wave lengths
1) Red has the longest wavelength (and the lowest frequency and energy)
2) Violet has the shortest wavelength (and the highest frequency and energy)
Define monochromatic light
single-wavelength light
Main regions of the electromagnetic spectrum
1) Radiowaves
2) Microwaves
3) Infrared
4) Visible light waves
5) Ultra violet
6)X-Ray
7) Y-Ray
Y rays usage
1) Also known as gama rays
used in treating cancer
2) sterilising medical instruments
Give examples of transverse waves
Light and radio
Give examples of longitude waves
Sound
Ultrasound
Which type of waves cannot travel in a vaccum
Longitude waves needs a medium to travel through
Draw a diagram of a longitude wave and label compression, wave lengthm and rarefraction
Compression is the high density area
Rarefraction is the low density area
Wave length starts from 1 compression to the next compression
Speed of light in air
340m/s
Refractive index formula with speed
Speed of light in vacuum /speed of light in material
Light slows down as it enters glass block explain what happens to light in terms of wavefronts
One side of wave front slows down before the other side
The wavefront bends at the boundary
This causes the wave to bend towards the normal
Describe a method of using water waves to demonstrate refraction [4]
1) Generate waves in a tank filled with shallow water.
2) Place a flat object under the surface of the water to change the depth partway along the tank.
3) Ensure that the waves are hitting the boundary of the shallower water at a non-perpendicular angle. 4) This will cause the waves to change direction as a result of their change in speed
How to measure the speed of sound in air [5]
1) Produce sharp sounds used for measurement
2) Use a suitable reflecting surface from which to reflect the sound off
3) Measure the distance travelled by sound
4) Measure the time for sound to travel the measured distance
5) Use speed = distance / time equation to calculate the speed of sound; [1 mark]
Define light dispersion
When light travels through a triangular prism, a band of colour, spectrum is oberseved. Because different colour has a different refraction due to different frequencies
Speed of light in air
3.0 × 108 m/s
Investigating Reflection
1) Reflection can be shown by the waves hitting a plane (straight) surface, such as a wall or mirror
2)
Refractive Index & Critical Angle formula
n = 1/sin c
Explain the properties of X-rays that make them useful in airport security [2]
1) X-rays are transmitted through less dense materials
2) absorbed by denser materials
explain why γ-rays are dangerous to living things [2]
1) Gamma rays are ionising high-energy
2) Gamma rays may damage or mutate cells
3) Gamma rays may cause radiation burns
Why is Short wavelength visible light and infrared radiation are used to achieve high rates for broadband
1) Radiation with a short wavelength has a high frequency
2) More information / data is transferred per second
WHy is X ray dangerous in medical operations and why is visible lights preferred [3]
1) X-rays penetrate soft-tissue
2) Visible light is reflected by soft tissue
3) X-rays may cause internal damage
Draw the path of visible light along the fibre from one end to the other in an optical fibre
Angles of incidence and reflection are equal (by eye) in each total internal reflection eoughly 90 degrees
why does light not reach blockage at 50 degrees [3]
1) The angle of incidence is less than 50°
2)At the point where the fibre bends / turns the corner
3)(Therefore) the light is refracted / leaves the fibre
State a typical value for the speed of sound in a liquid
A value in the range of 900 m/s to 2000 m/s
Explain how an echoe is formed
When sound waves reflect of hard surfaces
Define pitch [2]
1) Highness or lowness of a tone
2) High pitch = high frequency
Low pitch = low frequency
Define volume [2]
1) Loud or quietness of sound
2) High amplitude = loud volume
Low amplitude = quiet volume
Human hearing range
20hz - 20000hz
What is the name given to the low frequencies below 20hz
Infrasound
What is the name given to high frequencies above 20,000hz
Ultrasound
Explain, in terms of diffraction, why a car radio may pick up low frequency radio signals but
not pick up high frequency radio signals when the car is travelling behind a hill.
1)High frequencies have short wavelengths
2) Short wavelengths diffract less
Explain why the rays in optic fibre does not leave the fibre
1) The incidence angle is greater than critical angle so internal reflection occurs
Speed of sound formula
2xdistance to the wall/time taken
Speed of sound in liquid
1500m/s
Speed of sound in solid
5000 m/s
The sound wave passes from the end of the beam into air state 2 differences in wavelength and speed
both decrease
