Waves Flashcards
Longitudinal waves
Where the particles vibrate parallel to the direction of the wave travel (and energy transfer). These waves show areas of compressions and rarefactions
Transverse waves
Where the particles vibrate perpendicular to the direction of the wave travel (and energy transfer). These waves show areas of crests (peaks) and troughs
Amplitude
Is its height, measured from the middle of the wave to its top (or from the middle to its bottom)
Wavefront
A useful way of picturing waves from above: each wavefront is used to represent a single wave
Frequency
Is the number of waves passing a point (or being created or received) every second - it is helpful to think of it as being the waves per second. Measured in Hertz
Wavelength
Is the distance from a point on one wave to the same point on the next wave. Usually, this is measured from the top of one wave to the top of the next wave. Measured in metres (a distance)
Period of a wave
The time it takes for two consecutive crests (one wavelength) to pass a specified point. The wave period is often referenced in seconds, e.g. one wave every 6 seconds
What does a wave transfer?
They transfers energy from one place to another without transferring matter
Wave speed equation
Wave speed = frequency × wavelength
v = f × λ
Frequency equation
Frequency = 1/time period
Use the relationships in different contexts in terms of sound waves and electromagnetic waves
Doppler Effect
The apparent change in wavelength and frequency of a wave emitted by a moving source
Explain why there is a change in the observed frequency and wavelength of a wave when its source is moving relative to an observer (Doppler Effect)
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.
Reflection
A wave hits a boundary between two media and does not pass through, but instead stays in the original medium
Refraction
A wave passes a boundary between two different transparent media and undergoes a change in direction
Why are all waves Reflected and Refracted?
Order of Electromagnetic Spectrum
Radio, microwave, infrared, visible light, ultraviolet, x-ray, and gamma ray radiations (Roger, Might, Interestingly go on, Vacation, Using an, X-model while, Giggling)
Order of Electromagnetic Spectrum (in terms of decreasing wavelength and increasing frequency)
Radio wave uses and effects
Broadcasting and communications
Microwave uses and effects
Cooking and satellite transmissions
Internal heating of body tissue
Infrared uses and effects
Heaters and night vision equipment
Skin burns
Visible light uses and effects
Optical fibres and photography
Ultraviolet uses and effects
Fluorescent lamps
Damage to surface cells and blindness
X-ray uses and effects
Observing the internal structure of objects and materials, including for medical applications
Gamma rays uses and effects
Sterilising food and medical equipment cancer, mutation
Law of Reflection
When a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection
Investigate the refraction of light, using rectangular blocks, semi-circular blocks and triangular prism
- 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.
Relationship between refractive index, angle of incidence and angle of refraction equation
n = sin i/sin r
- 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.
Role of total internal reflection in transmitting information along optical fibre and prisms
To capture the light transmitted in optical fibre and confine the light to the core of the fibre
Critical angle c
The angle of incidence to which the angle of refraction is equivalent to
Relationship between critical angle and refractive index equation
sin c = 1/n
