Waves

Question 0

What is one use of a polarising filter?

Answer 0

Plastic stress/strain analysis

Question 1

What is a wave?

Answer 1

A periodic disturbance in a medium

Question 2

What is the relationship between intensity and amplitude?

Answer 2

Intensity is directly proportional to amplitude

Question 3

What is malus’s law?

Answer 3

Intensity = initial intensity of light x cos^2 theta

Theta is the angle between the filter and the light relative to the plane of the initial polarised light.

Question 4

How do you calculate intensity?

Answer 4

Intensity = power / area

Area = 4pi x r^2

Question 5

What is intensity?

Answer 5

Intensity is the amount of energy arriving in an area of 1m^2 of the surface in 1 second

Question 6

What is the unit of intensity?

Answer 6

Wm^-2

Question 7

What is the principle of superposition?

Answer 7

When two or more waves overlap, the resultant displacement at a point is equal to the vector sum of the individual displacement at that point.

Question 8

What are the conditions that waves must have in order to be coherent

Answer 8

Same frequency

Constant phase difference

Question 9

What is path difference

Answer 9

Path difference is the extra distance travelled by waves from one source compared to another

Question 10

V out = ?

Answer 10

R2/R1 + R2 x V in

Question 11

Phase difference = ?

Answer 11

The fraction if a complete cycle between two points on a wave

Question 12

What is phase

Answer 12

Phase is the position of a wave, or a point on a wave at a particular moment in time, measured in radians

Question 13

V = ?

When given frequency and wavelength

Answer 13

V = f x lambda

Question 14

What are the three key things to form a standing wave

Answer 14

You reflect a wave.
They must have the same frequency and amplitude.
They interfere.

They produce a wave with nodes and antinodes

Question 15

what is the range of wavelength of visible light?

Answer 15

Red 700nm to Violet 400nm

Question 16

what is the wavelength of gamma rays

Answer 16

10^-12 m

Question 17

what is the wavelength of X rays

Answer 17

10^-8

Question 18

what is the wavelength of ultraviolet

Answer 18

10^-7

Question 19

what is the wavelength of infra red

Answer 19

10^-4

Question 20

Intensity is?

Answer 20

Directly proportional to amplitude^2

i=Ka^2

Question 21

What is the Double-slit interference equation and what are its components?

Answer 21

Y=ax/D
Where Y is wavelength
Where a is slit separation
Where x is fringe width
Where D is the distance between the slit barrier and the screen

Question 22

What are the two path differences that can occur and what do they cause?

Answer 22

Path difference = nY means waves arrive in phase, causing constructive interference and a bright fringe.

Path difference = (n+1/2)Y mean waves arrive in antiphase, causing destructive interference and a dark fringe.

Question 23

What are the conditions that need to be met for two interfering waves to be coherent?
Give an example of coherence.

Answer 23

The waves must be in phase / have a constant phase difference
Therefore have the same frequency

Laser light is coherent

Question 24

What are the conditions that must be met for observable interference to occur

Answer 24

Coherent wave sources, I.e. Same frequencies

The interfering waves should be of the same amplitude to ensure good contrast between bright and dark fringes.

Question 25

What is the equation for diffraction gratings?

Answer 25

dSin@ = nY
Where d is the grating spacing, d=1/number of lines per mm.
Where @ (theta) is the diffraction angle
Where n is the diffraction order (n=1,2,3…)
Where Y is the wavelength of the light

Question 26

What are the advantages of using multiple slits over a double slit

Answer 26

Interference fringes obtained with double slits are faint and blurred (no definite edge)
Whereas a diffraction grating overcomes these problems. The maxima are brighter because more slits = more transmitted light.
The maxima are very sharp because constructive interference only happens in certain precise directions.

Question 27

The Young’s double slit experiment gives evidence in…

Answer 27

In favour of the wave theory of light as it demonstrates light being diffracted which only waves can do, not particles.