Waves and Photons Flashcards
What does ‘out of phase’ mean?
Where 2 waves have different multiples of the wavelength
What does ‘in phase’ mean?
Where 2 waves have the same a multiple of the wavelength
What is the equation for a wave that is in phase?
N(lander)
What does N stand for in the equations?
Each full wave
What is path difference?
The distance between the lengths the waves take
What is the principle of superposition?
Where two or more waves meet, the sum of the vector of displacements that the individual waves would cause at a point
What is constructive superposition?
Where two or more waves are in phase of each other or have a radian of 0 degrees so will arrive in phase
What are coherent waves?
Waves that have the same frequency and maintain a constant phase relationship
What is a destructive wave?
Two waves that are of equal frequency but opposite phase arrive at a point
What is a wave front?
A line that connects all the waves in a line
How do you work out phase difference?
Find the path difference
Divide that by the wavelength
x the answer by 2pirad (because it’s one full wave)
that would be it’s total out of sync or in sync
What is the thin lens equation?
1/U + 1/V - 1/F
What does the U stand for in the thin lens equation?
Distance from the object to the lens
What does the V stand for in the thin lens equation?
Distance from the lens to the image
What does the F stand for in the thin lens equation?
Distance from the lens to the focal point
With concave lenses, what must always be true?
The lens will produce a virtual and upright image
What is the difference between a concave and convex lens?
A convex lens you can project the image onto a screen
Concave lens is a virtual image where the lines would appear to meet
What does Huygens construction describe?
A wave forms at a wavefront and has a spherical shape and travels at the same speed and wavelength
What is the wavelength of the fundamental harmonic
2L
Why does a pencil look bent in water?
The water is more dense than the air so the image doesn’t form as fast so appears to bend round the image
What is the definition of incident?
Where the ray first travels from onto an object
Define Principal axis
The middle axis which can’t always be seen. Centre of the lens and perpendicular to it
Define the normal
Line perpendicular to the boundary
What is a focal point?
Where Parallel rays meet at a point`
What is focal length?
Distance between the lens and focal point
What is the critical angle?
The angle at which refraction doesn’t take place and instead internal reflection does
What does phase mean?
A point in the wave cycle
Define a transverse wave
A wave that oscillates perpendicular to the direction of propagation/ energy transfer
Define a longitudinal wave
A wave that oscillates parallel to the direction of energy transfer
Define amplitude
The maximum extent of a vibration of a wave
Define interference
Two waves superpose to form a resultant waves of greater less or equal amplitude
Define phase difference
The position in a wave
Define a real image
Where two waves meet from a lens. Can be projected on a screen
Define a virtual image
Image formed from apparent divergence of waves
Define plane polarisation
Restricting the vibrations of EM radiation to one direction
Define diffraction
Bending of light around an object
Define the pulse echo technique
Non destructive testing using ultrasound waves to detect defects in materials
List diffraction experiments
Using a laser through tiny slits onto a wall and measuring the distance in between the dots produced
What is intensity of radiation?
How much energy reaches an area per second
Define path difference
The difference between two waves
How do noise cancelling headphones work?
They produce a wave that is 180 degrees out of phase to the surrounding waves of sound so that they superpose destructively (destructive interference) to cause an overall output of 0
What is a node?
A point along the wave where it has a minimum amplitude
What is an antinode?
A position of maximum amplitude on a wave
