Section 4: Waves and Optics Flashcards

Question

Focal length (f)

Answer 1

Focal length for converging mirror/lens is +ve | Focal length for diverging mirror/lens is -ve

Answer 2

Magnification +ve for upright image -ve for inverted image

Answer 3

Use a -ve sign for d(o.2) in the equation

Answer 4

A disturbance that moves itself and energy but not matter from one place to another in a medium Particles in the medium vibrate about their original position

Answer 5

Particlesi n the medium move in a direction perpendicular to the direction of travel of the wave

Answer 6

Particles in the medium move in a direction parallel to the direction of travel of the wave

Answer 7

Periodic | i.e. they repeat themselves

Answer 8

Distance from a point on the wave to the next corresponding point on the wave Units: m

Answer 9

Max displacement from the centre line (equilibrium position) | Units: appropriate to type of wave, e.g. m, V, Pa

Answer 10

Time for one complete vibration | Units: s

Answer 11

No of vibrations per second | Units: Hz

Answer 12

Rate of movement (propagation) of a wave

Answer 13

Describes at what stage of the cycle as wave is; going up or down, from the reference value

Answer 14

Particles in a wave considered to be in phase when they execute the same motion (same stage of their cycle) at the same time

Answer 15

Half a cycle out of phase | Execute the exact opp motion at the same time

Answer 16

Power per unit area

Answer 17

Used to compare intensities

Answer 18

Adding 10 dB = multiplying I by 10 | 3dB is approx 2x intensity

Answer 19

The change in the observed f of a wave due to the motion of the wave source relative to the observer

Answer 20

Increase in f, decrease in wavelength

Answer 21

Decrease in f, increase in wavelength

Answer 22

The resultant waveform when diff waves meet at the same point in space at the same time is the sum of their individual displacements (heights)

Answer 23

2 waves of identical f and A arriving at the same point exactly in phase Resultant wave has twice the A but same f and wavelength

Answer 24

2 waves of identical f and A arriving at the same point exactly out of phase Resultant wave has zero amplitude

Answer 25

2 waves of identical f but diff A arriving at the same point exactly out of phase Resultant wave has same wavelength and f, but its A is the difference of the amplitudes of the individual waves

Answer 26

Where 2 waves have *slightly* diff frequencies and superimpose Overall amplitude = beat frequency f(B)

Answer 27

The f at which an object vibrates when it's set to vibrate and then left free

Answer 28

An object is forced to vibrate at a certain f by constantly applying a periodic force

Answer 29

Depends on frequency of the forcing | If forced at natural f, the A can grow huge

Answer 30

Tendency of a system to oscillate at larger amplitudes at some f than others Max amplitude = when system forced to vibrate at its natural frequency = at resonance

Answer 31

Tuned mass dampers stabilise against violent motion caused by forced vibrations

Answer 32

The bending of a wave around an obstacle or the edges of an opening

Answer 33

Sources that maintain the constant phase difference

Answer 34

``` PD = 0 or integer --> constrictive interference PD = 1/2 wavelength --> destructive interference ```

Answer 35

``` PD = 1/2 wavelength --> constructive interference PD = 0 or integer --> destructive interference ```

Answer 36

``` Maxima = bright fringes, PD = 0 or integer Minima = dark fringes, PD = half integer ```

Answer 37

2-point objects are just resolved when the first dark fringe in the diffraction pattern of one falls directly on the central bright fringe in the diffraction pattern of the other

Answer 38

For incident angles other than 0, unpolarised light becomes partially polarised in reflecting from a non-metallic surface

Answer 39

When unpolarised light is incident on a non-metallic surface at the Brewster angle (θB), the reflected light is 100% polarised in the direction parallel to the surface The angle between the reflected and refracted rays is 90 degrees

Answer 40

``` A = nucleon number; no of protons and neutrons Z = proton number; no of protons ```

Answer 41

The probability that any one nucleus out of N nuclei decays in any one second is a constant λ (decay constant)

Answer 42

The time taken for the no of undecayed nuclei to be reduce to half its original number

Answer 43

A = Z + N (no of protons + no of neutrons)

Answer 44

Nuclei that contain the same no of protons but diff no of neutrons

Answer 45

The mutual repulsion of protons tends to push the nucleus apart The strong nuclear F acts over short ranges and binds the protons and neutrons tgt

Answer 46

As the nuclei gets larger, more neutrons are required for stability

Answer 47

Where unstable nuclei can break apart on their own with a predictable probability

Answer 48

The nucleus ejects a He nucleus to become a smaller and more stable nucleus

Answer 49

A neutron is converted to a proton (or vice versa) to become a more stable nucleus Releases energy - carried away by a neutrino

Answer 50

The nucleus gives off energy in the form of a gamma ray to reach a lower energy state

Section 4: Waves and Optics Flashcards

(74 cards)