3.3 Waves

Question 1

Amplitude

Answer 1

Max displacement of oscillating particle from equilibrium position

Question 2

Antinode

Answer 2

Fixed point on stationary wave where amplitude is maximum

Question 3

Coherent

Answer 3

Constant phase difference and same frequency

Question 4

Critical angle

Answer 4

The angle of incidence of a light ray must exceed this angle for total internal reflection to occur

Question 5

Cycle

Answer 5

Interval for an oscillating particle from a certain displacement and velocity to the next time the particle has identical displacement and velocity

Question 6

first harmonic

Answer 6

pattern of stationary waves on a string when it oscillates at lowest possible frequency

Question 7

frequency

Answer 7

number of cycles of a wave that pass a point per second

Question 8

longitudinal waves

Answer 8

waves with particles that oscillate parallel to the direction of propagation of the wave

Question 9

laser

Answer 9

produces coherent, parallel beam of monochromatic light

Question 10

node

Answer 10

fixed point on a stationary wave where displacement is zero

Question 11

path difference

Answer 11

difference in the distances from two coherent sources to an interference fringe

Question 12

period

Answer 12

time for one complete cycle of a wave to pass a point

Question 13

phase difference

Answer 13

the fraction of a cycle between the oscillations of 2 oscillating particles - measured in radians

Question 14

plane-polarised waves

Answer 14

transverse waves that oscillate in one plane only

Question 15

progressive waves

Answer 15

waves which travel through a substance or space if electromagnetic

Question 16

refraction

Answer 16

change of direction of a wave when it crosses a boundary where its speed changes e.g new medium

Question 17

refractive index

Answer 17

speed of light in free space

Question 18

spectrometer

Answer 18

instrument used to measure light wavelengths very accurately

Question 19

stationary waves

Answer 19

wave pattern with nodes and antinodes formed when 2 or more progressive waves of same frequency and amplitude pass through eachother

Question 20

superposition

Answer 20

effect of 2 waves adding together when they meet

Question 21

total internal reflection

Answer 21

light ray will totally internally reflect at boundary of 2 substances when boundary has new substance with lower refractive index and the angle of incidence is greater than the critical angle

Question 22

transverse waves

Answer 22

wave where direction of oscillations of the particles of the waves are perpendicular to the direction of propagation of the wave

Question 23

wavefronts

Answer 23

lines of constant phase

Question 24

wavelength

Answer 24

least distance between 2 adjacent vibrating particles with the same displacement and velocity at the same moment in time

Question 25

Young’s fringes

Answer 25

parallel bright and dark fringes observed when light from a narrow slit passes through 2 closely spaced slits

Question 26

period

Answer 26

time for one complete cycle of a wave to pass a fixed point

Question 27

resonant frequency

Answer 27

the frequency of an oscillating system in resonance

Question 28

applications of polarisers

Answer 28

sunglasses lenses - reduce glare, camera lenses - reduce glare, 3D glasses lenses - improve picture quality

Question 29

single slit diffraction pattern

Answer 29

large central maxima twice width of subsidiary minima, decreasing height of subsidiary minima

Question 30

effect on diffraction pattern of slit width

Answer 30

larger slit width means narrower central maxima / subsidiary minima closer together

Question 31

xray wavelength

Answer 31

1nm

Question 32

optical fibre

Answer 32

thin, flexible transparent fibre used to carry light pulses from one end to another

Question 33

modal dispersion

Answer 33

lengthening of a light pulse as it travels along optical fibre due to continual total internal reflection of waves meaning some rays travel longer distance than others in fibre

Question 34

interference

Answer 34

formation of points of cancellation and reinforcement where two coherent waves pass through eachother

Question 35

natural frequency

Answer 35

frequency of free oscillations of an oscillating system