11 - Definitions

Question 1

Progressive wave

Answer 1

An oscillation that travels through matter. Transfers energy from one place to another

Question 2

Transverse wave

Answer 2

Oscillations are perpendicular to the direction of energy. Has peaks and troughs where oscillator particles are at maximum displacement from their equilibrium position.

Question 3

Displacement

Answer 3

Distance from equities position (m)

Question 4

Amplitude

Answer 4

Maximum displacement from equilibrium position. (m)

Question 5

Wavelength

Answer 5

Minimum distance between two points. e.g peaks or troughs.

Question 6

Period of oscillation

Answer 6

Time taken for one oscillation or for a wave to move one whole wavelength past the given point.

Question 7

Frequency

Answer 7

Number of wavelengths passing a given point per unit of time.

Question 8

Wave speed

Answer 8

Distance travelled by the wave per second

Question 9

Wave speed =

Answer 9

Frequency x wavelength

Question 10

Frequency =

Answer 10

1 / period of the wave (S)

Question 11

Phase difference

Answer 11

Difference between the displacement of particles along the wave, or the difference between the displacements of particles in different waves.

Question 12

In phase

Answer 12

Phase difference of 0. In step with each other.

Question 13

Anti-phase

Answer 13

Oscillating completely out of step with each other.

Question 14

Phase difference equation

Answer 14

Distance between the waves or points
___________ X 360

Wavelength.

Question 15

Law of reflection

Answer 15

Angle of incidence = angle of reflection

Question 16

Refraction defined

Answer 16

Wave changes direction, as it changes speed passing though a different medium.

Refracts towards normal.

Question 17

Refractive Index defined

Answer 17

Different materials refract light by different amounts. The angle the line in bent at depends on the relative speed of light through the material

Question 18

Refractive index =

Answer 18

The speed of light in vacuum
__________________________

The speed of light though the material

Question 19

Diffraction

Answer 19

When waves pass through a gap or travel around an obstacle, they spread out.

Speed, wavelength and frequency don’t change.

Occurred when gap is smaller than wavelength

Question 20

Inverse Square - Intensity

Spread out equally

Answer 20

Total radiant power (P) at a distance (r) from the source is spread out over an area = to the surface area of a sphere.

I = P/ 4(pie)r^2

Question 21

Polarisation

Answer 21

Only waves oscillating on one plane are able to get through filters.

Most naturally occurring EM waves are unpolarised, meaning they are oscillating on different planes.

Question 22

Intensity is proportional to:

Answer 22

(Amplitude)^2

Question 23

Longitudinal waves can’t be:

Answer 23

Plane polarised

Question 24

Longitudinal wave

Answer 24

Wave oscillations are parallel to the direction of energy transfer.

Question 25

Oscilloscope

Answer 25

Shows a graph of pd against time, of a signal.

Horizontal square represents specific time interval. = Time base

To get frequency use timebase to determine time period of the wave.

F=1/T

Question 26

Total internal reflection

Answer 26

When the incidence angle is at the critical angle in a medium with a higher RI ,the ray will reflect back into the slow medium.

Higher the refractive index, the lower the critical angle

SinC = 1/n

Question 27

Critical angle =

Answer 27

Refractive angle of 90 degrees,

So the light can’t escape the slower medium.