Waves (Paper 1) Flashcards
What are transverse waves?
oscillation of particles (or fields) are at right angles to the direction of energy
transfer
What are longitudinal waves?
oscillation of particles is parallel to the direction of energy transfer
● These are made up of compressions and rarefactions and can’t travel in a vacuum.
● Sound is an example of a longitudinal wave, and they can be demonstrated by pushing a
slinky horizontally.
What is a polarised wave?
A polarised wave oscillates in only one plane. Only transverse waves
can be polarised. Polarisation provides evidence for the nature of transverse waves because polarisation can only occur if a wave’s oscillations are perpendicular to its direction of travel
What are examples of polarisation?
Polaroid sunglasses are an application of polarisation. They reduce glare by blocking partially polarised light reflected from water and tarmac, as they only allow oscillations in the plane of the filter, making it easier to see.
What is superposition?
Superposition is where the displacements of two waves are combined as they pass each other, the resultant displacement is the vector sum of each wave’s displacement.
What is a stationary wave?
No energy is transferred by a stationary wave.
A stationary wave is formed from the superposition of 2 progressive waves, travelling in
opposite directions in the same plane, with the same frequency, wavelength and amplitude.
What is path difference?
Path difference is the difference in the distance travelled by two waves
What is a coherent light source?
A coherent light source has the same frequency and wavelength and a fixed phase difference.
Explain young’s double slit experiment
Use 2 coherent light sources in order to make an interference pattern or one light with a double slit.
What are the steps to young’s double slit experiment?
Shine a coherent light source through 2 slits about the same size as the wavelength of the laser light so the light diffracts
● Each slit acts as a coherent point source making a pattern of light and dark fringes. Light fringes are formed where the light meets in phase and interferes constructively, this occurs where the path difference between waves is a whole number of wavelengths (nλ, where n is an integer). Dark fringes are formed where the light meets completely out of phase and interferes destructively, this occurs where the path difference is a whole number and a half wavelengths ((n+½)λ).
What does white light shone through a double slit do compared to other light sources?
Using white light instead of monochromatic laser light gives wider maxima and a less intense diffraction pattern with a central white fringe with alternating bright fringes which are spectra, violet is closest to the central maximum and red furthest.
What is the evidence for the wave nature of light?
It was provided by Young’s double slit experiment because diffraction and interference are wave properties, and so proved that EM radiation must act as a
wave (at least some of the time).
How does gap affect diffraction?
Smaller gap=reflected waves
Gap equal to wavelength=most diffraction
Gap larger than wavelength=less noticeable diffraction
Explain what’s seen when monochromatic light is shone through a single slit
It forms an interference pattern of light and dark fringes. The pattern has a bright central fringe, which is double the width of all other fringes. The bright fringes are caused by constructive interference where the waves meet in phase and the
dark fringes are caused by destructive interference where waves arrive completely out of phase
What occurs when white light is shone through a single slit?
As white light is made up of all colours, therefore all different
wavelengths of visible light, the different wavelengths of light are all diffracted by different amounts so you get a spectrum of colour in the diffraction pattern. The diffraction pattern for white light has a central white maximum with alternating bright fringes which are spectra, violet is
closest to the central maximum and red furthest away
