Waves

Question 1

What is a wave?

Answer 1

A periodic disturbance of particles in a material or in space.

Question 2

What is a transverse wave?

Answer 2

Particle oscillations are perpendicular to the direction of propagation of the wave.

Question 3

What is a longitudinal wave?

Answer 3

Particle oscillations are parallel to the direction of propagation of the wave.

Question 4

What are mechanical waves?

Answer 4

Oscillations of particles in a physical medium.

Question 5

What are Electromagnetic (EM) waves?

Answer 5

Waves produced by the acceleration of charged particles, transmit through vacuum.

Question 6

What is the equation of wave speed?

Answer 6

Speed = Frequency x Wavelength

Question 7

What is the frequency of a wave?

Answer 7

Number of waves passing a point in one second.

Question 8

What is the period of a wave?

Answer 8

Time for a full cycle.

Question 9

What is unpolarised light?

Answer 9

Waves at all different possible planes at 90 degrees to the source.

Question 10

What is polarised light?

Answer 10

Wave is only oscillating in one plane.

Question 11

What is superposition?

Answer 11

Two or more waves overlap, the resultant displacement at a point is the sum of the individual waves at that point (waves add up).

Question 12

What is constructive interference?

Answer 12

Waves have the same sign displacement when they overlap (reinforcement).

Question 13

What is destructive interference?

Answer 13

Waves have opposite sign displacement where they overlap (cancellation).

Question 14

What is diffraction?

Answer 14

Wave spread out after passing through a gap.

Question 15

What are coherent waves?

Answer 15

Two waves with the same frequency and wavelength and have a constant phase difference.

Question 16

What is a monochromatic wave?

Answer 16

Single wavelength / frequency being produced.

Question 17

What is the diffraction grating equation?

Answer 17

distance between slits x sin(angle) = order x wavelength

Question 18

What is a standing wave?

Answer 18

Forward waves interact with reflected waves (coherent waves).

Question 19

Where do nodes occur?

Answer 19

Areas of destructive interference.

Question 20

Where do antinodes occur?

Answer 20

Areas of constructive interference.

Question 21

What part of a standing wave is formed at a closed end of a tube?

Answer 21

Node

Question 22

What part of a standing wave is formed at an open end of a tube?

Answer 22

Antinode

Question 23

What is refraction?

Answer 23

Incident ray enters more optically dense medium, slows down and bends towards the normal.

If it enters a less optically dense medium, it speeds up and bends away from normal.

Question 24

How do you find the refractive index of a substance?

Answer 24

Speed of light in vacuum / speed of light in substance

Question 25

When does total internal reflection occur?

Answer 25

If the incident angle is greater than the critical angle.

Question 26

What happens if the incident angle is equal to the critical angle?

Answer 26

Light is refracted along the boundary.

Question 27

What is the purpose of cladding in optical fibres?

Answer 27

Protects fibre / core from damage. Lowers critical angle.

Question 28

What is signal absoprtion?

Answer 28

Reduces amplitude over time.

Question 29

What is signal dispersion?

Answer 29

Pulse broadening causes modal and material dispersion.

Question 30

What is modal dispersion?

Answer 30

Different path lengths because of the different angles of entry.

Question 31

What is material dispersion?

Answer 31

Different wavelengths travelling at different speeds (red is fastest).