Physics unit1

• What is the formula for wave frequency?

  f = 1.5
• How do particles move in longitudinal waves?

  Particles move backwards and forwards
• What do longitudinal waves show in terms of pressure?

  They show areas of compression and rarefaction
• Give an example of longitudinal waves.

  Sound waves
• How do particles move in transverse waves?

  Particles move up and down
• Name an example of transverse waves.

  Electromagnetic waves
• What is a characteristic of electromagnetic waves?

  They can travel through a vacuum
• What is the lowest frequency of visible light?

  Red light
• What is polarisation in light waves?

  Light oscillates at different angles
• What does a polarising filter do?

  Removes oscillations at 90° to the filter
• What happens when light passes through a second polarising filter aligned with the first?

  The waves can pass through
• What happens if the second filter is turned to 90° relative to the first?

  It will stop the light from passing through
• What is the wave speed equation frequency?

  3.27 × 10¹⁴ Hz
• What is phase in wave terminology?

  Position of a point in time on a wave's cycle
• What is phase difference?

  Difference in phase angle between two waves
• What is the phase difference between points M and N?

  $\pi$ radian
• What is the phase difference between points O and P?

  $\pi$ radian
• What does "in phase" mean?

  Phase difference of 0
• What does "antiphase" mean?

  Phase difference of $\pi$
• What are coherent waves?

  Waves with constant phase difference and same frequency
• What is superposition in wave theory?

  Resultant displacement equals vector sum of displacements
• What leads to constructive interference?

  Waves in phase
• What leads to destructive interference?

  Waves in antiphase
• What is path difference?

  Difference in distance travelled by two waves
• What do interference patterns contain?

  A series of maxima and minima
• What occurs at maximum in interference patterns?

  Waves interfere constructively
• What occurs at minimum in interference patterns?

  Waves interfere destructively
• What is diffraction?

  Waves spread out when passing through a gap
• What are diffraction gratings?

  Plates with many close, parallel slits
• What happens at bright areas in diffraction gratings?

  Light of the same wavelength is in phase
• What happens at dark areas in diffraction gratings?

  Light is out of phase
• What is white light composed of?

  A mixture of different frequencies of light
• What is the ground state of an atom?

  Lowest energy state possible
• What happens to electrons when atoms are heated?

  Electrons are promoted to higher energy levels
• What happens when excited electrons fall back to the ground state?

  They lose energy and emit light
• What is the result of different wavelengths diffracting at different angles?

  Constructive interference produces colored bands
• Why do different atoms produce characteristic patterns of lines?

  They have different numbers of electrons
• What is the equation for energy in quantum theory?

  E = hf
• What is Planck's constant?

  6.63 x 10^-34 Js
• What is a standing wave?

  Energy is stored rather than transferred