Unit2.4)The Nature of waves

Question 1

Two types of progressive waves?

Answer 1

Transverse and longitudinal

Question 1

Define the term progressive wave?

Answer 1

A pattern of disturbances(Waves)travelling through a medium and carrying energy with it, as the wave propagates(travels) it transfers energy from one medium to another.
(Progressive waves transfer energy without any transfer of matter(or particles).

Question 2

What is a longitudinal wave?

Answer 2

A wave in which the oscillations of the particles are parallel to the direction of travel of the wave.(Longitudinal waves do not move in the direction perpindicular to the direction of travel)
These waves have rarefactions(areas of low pressure) and compressions (areas of high pressure).

Question 3

What is a transverse wave?

Answer 3

Waves where the oscillations of the particles are perpindicular(at right angles) to the direction of travel of the wave.

Question 4

Example of a transverse wave?

Answer 4

Electromagnetic wave.

Question 5

Example of a longitudinal wave?

Answer 5

Sound waves.

Question 6

Displacement of a wave meaning?

Answer 6

The distance of a particle from its equilibrium position at any instant

Question 7

Amplitude?

Answer 7

This is the maximum value of displacement.

Question 8

Wavelength?

Answer 8

Minimum distance between two points on the wave which are oscillating in phase.

Question 9

Frequency?

Answer 9

The number of cycles of a wave that pass a given point in one second(number of oscillations per second by any particle in the medium through which the wave is travelling).

Question 10

Period(T)?

Answer 10

Time taken for one complete cycle.

Question 11

If knowing the time period(T)of a wave, how would you calculate the speed and frequency of the waves?

Answer 11

frequency = 1/period
speed = wavelength/period
(or speed = frequency x wavelength.)

Question 12

What does a polarising filter do?

Answer 12

Polarising filters only allow oscillations in one direction to pass through. Oscillations in all other directions are absorbed. The light that has passed through is now said to be polarised light or plane polarised light.

Question 13

What is a polarised wave?

Answer 13

a transverse wave in which particle oscillation occur in only one of the directions or planes at right angles to the direction of wave propagation.

Question 14

Can you polarise longitudinal waves?

Answer 14

No it is impossible to polarise longitudinal waves.

Question 15

What happens if polarised light is directed through two polaroid filters?

Answer 15

If the polaroid sheets are lined up parallel it will be a maximum(brightness).
It will be 0(darkness) when the polarised sheets are lined up perpindicular to one another.

Question 16

How is polarisation used as evidence of the nature of transverse waves?

Answer 16

Polarisation only occurs if a waves oscillations are perpindicular to its direction of travel(this is the same as transverse waves meaning only transverse waves can be polarised.

Question 17

How is polarisation used in antennas?

Answer 17

Tv and radio signals are usually plane-polarised by the orientation of the rods on the transmitting areal, so the receiving areal must be aligned in the same plane of polarisation to receive the signal at full strength.

Question 18

What is ‘phase’?

Answer 18

The position of a certain point on a wave cycle(units are radians, degrees or fractions of a cycle).
If the two waves are in phase, there is constructive interference: the resultant amplitude is large, equal to the sum of the two wave amplitudes.

Question 19

How can you find the out the time period of a wave using its frequency?

Answer 19

T=1/f

Question 20

What is the speed of a wave with frequency 10GHz and wavelength 6cm?

Answer 20

c=f λ
c=(10x10^9)x(6x10^-2)
c=6x10^8 m/s

Question 21

what are wave fronts?

Answer 21

Wave fronts are an imaginary surface representing corresponding points in a wave vibrate simultaneously. All points on the wave fronts are in phase. The wave fronts travel radially from a source and therefore the direction of travel of the waves(wave propagation directions) are at right angles to wave fronts.

Question 22

What is anti phase?

Answer 22

If the two waves are in antiphase, there is destructive interference: the resultant amplitude is small, equal to the difference between the two wave amplitudes.

Question 23

Graphs of displacement against time, and
displacement against position for transverse
waves only

Answer 23

Certainly! When studying transverse waves, it’s common to analyze graphs of displacement against time and displacement against position. Let’s break down what these graphs represent:

1. Displacement vs. Time (Waveform):
   
   • This graph shows how the displacement (usually denoted by the letter $$y$$) of a particle varies with time as the wave passes through it.
   • The x-axis represents time (usually in seconds), and the y-axis represents displacement (usually in meters).
   • For transverse waves, the displacement oscillates perpendicular to the direction of wave propagation.
   • The waveform typically exhibits a sinusoidal pattern (e.g., sine or cosine function) due to the harmonic nature of waves.
2. Displacement vs. Position (Wave Profile):
   
   • This graph illustrates how the displacement of particles varies along the position (usually denoted by x) of the wave.
   • The x-axis represents position (usually in meters), and the y-axis represents displacement (also in meters).
   • For transverse waves, the displacement varies spatially as the wave travels.
   • The shape of the wave profile depends on the specific wave type (e.g., sine wave, triangular wave, etc.).

Remember that these graphs provide valuable insights into wave behavior, allowing us to understand properties like wavelength, frequency, and amplitude.