Waves Flashcards
When are longitudinal waves produced
When the vibrations are parallel to the axis
What do waves transfer?
Energy (NOT matter)
Compression
Region where the particles are closer
A region where the particles are farther apart
Rarefaction
What is the relationship between the amount of diffraction and wavelength
The longer the wavelength the more diffraction there is
Why is red light diffracted the most
Longer wavelength
What is the time period of a wave and what is it measured in
The time it takes for a source to produce one wave, measured in seconds
What is the frequency of a wave & what is it measured in?
The number of waves produced each second, hertz
What is the equation relating frequency (f) and time period (T)
f = 1 ➗ T
Or
T = 1➗f
The height of a sound wave is related to
The volume
The greater the amplitude..
The louder the sound
The amplitude
The maximum displacement of the wave from the undisturbed/equilibrium position
The number of waves produced is related to
The pitch or frequency
The wave equation
Wave speed = frequency x wavelength
Wavelength
The distance in metres from any point on the wave to where it repeats
When are transverse waves produced
When the vibrations are at right angles to the direction of energy
What is a wave
A vibration or disturbance transmitted through a material (a medium) or through space
Light waves are
Transverse
Shortest wavelength, highest frequency, highest energy
Gamma rays
Properties that all electromagnetic waves share 2
Transverse waves
Can travel through a vacuum
Longest wavelength, lowest frequency & lowest energy
Radio waves
Trough
Point on a wave with the lowest displacement
What is refraction
The bending of light when it enters a different medium
Why does the refractive index have no units?
It’s a ratio
When does TIR occur
When the angle of refraction is greater than 90 and the light cannot leave the medium
What’s normal?
An imaginary line that’s at right angles to the surface (at the point where light hits the surface)
Law of reflection
The angle of incidence equals the angle of reflection
Critical angle
The angle of incidence above which TIR occurs
Why do diamonds sparkle
Diamond has a very high refractive index and so a low critical angle which leads to more internal reflections
Why is a semicircular block used to demonstrate total internal reflection
The incident ray always hits the curved side of the block at 90* so there are no refraction effects as it enters the block, only when it leaves from the straight edge
Properties of image in plane mirror (4)
- laterally inverted
- virtual
- same size
- as far behind the mirror as the object is in front
Explain why a ray entering a glass block changes direction each time it crosses the air/glass boundary
As the ray of light enters the glass block, it slows down and is refracted towards the normal.
As the Ray leaves the glass block, its speed increases and it is refracted away from the normal
Why is white light dispersed
White light is composed of a mixture of colours. Because each colour travels at a different speed through the prism, they are refracted through different angles
Advantage of using prisms in a periscope rather than plane mirrors
The final image created by a prismatic periscope is likely to be sharper and brighter
What would happen to a ray of light inside an optical fibre if the outer glass had a higher optical density than the inner glass?
If the outer glass of an optical fibre had a higher refractive index, light within the fibre striking the boundary would be refracted and escape through the sides
Médical application of optical fibres
Endoscopes allow doctors to see inside the body, and make keyhole surgery possible
