Waves Key Definitions And Exact Values

Question 1

Wavelength of radio waves?

Answer 1

10 m

Question 2

Wavelength of microwaves?

Answer 2

10^-3 m

Question 3

Wavelength of infrared radiation?

Answer 3

10^-6 m

Question 4

Wavelength of visible light? Violet and red

Answer 4

Violet = 400nm, Red = 700nm
4-7x10^-7 m

Question 5

Wavelength of ultraviolet?

Answer 5

10^-8 m

Question 6

Wavelength of X-rays?

Answer 6

10^-10 m

Question 7

Wavelength of gamma rays?

Answer 7

10^-14 m

Question 8

Define displacement. Give the symbol
and unit.

Answer 8

Displacement is the distance from the equilibrium position in a particular direction; vector function; symbol s and unit in metres

Question 9

Define amplitude. Give the symbol
and unit.

Answer 9

Amplitude is the maximum displacement from the equilibrium position (can be +ve or -ve); symbol A, unit in metres

Question 10

Define wavelength. Give the symbol
and unit.

Answer 10

The minimum distance between two points on adjacent waves oscillating in phase; symbol is lambda, unit is metres

Question 11

Define the period of oscillation. Give the symbol and unit.

Answer 11

The period is the time taken for a full oscillation or a wave to move one whole wavelength to past a given point; symbol is T and unit is seconds

Question 12

Define frequency. Give the symbol
and unit.

Answer 12

Frequency is the number of wavelengths passing a given point per unit time; symbol is f and units are Hz

Question 13

Define wave speed. Give the symbol
and unit.

Answer 13

Wave speed is the distance travelled by a wave per unit time. Symbol is very (or c for speed of light) and unit is ms^-1

Question 14

Define a progressive wave

Answer 14

A progressive wave is an oscillation that travels through matter and transfers energy from one place to another without transferring any matter.

Question 15

What is the difference between mechanical and electromagnetic waves?

Answer 15

Mechanical waves require a medium to travel through and through particles oscillate about fixed positions.

On the other hand, electromagnetic waves do not require a medium and so can travel through vacuums - they transfer energy through vibrations of electric and magnetic fields. The changing magnetic field induces a changing electric field, forming an electromagnetic wave.

Question 16

List 3 common properties to electromagnetic waves

Answer 16

1. EM waves can travel through vacuums (they do not need a medium to transfer energy)
2. EM waves all travel at the same speed (the speed of light, c = 3 x 10^8 ms^-) in a vacuum
3. All EM waves are transverse waves

Question 17

List 3 differences between transverse waves and longitudinal waves

Answer 17

1. Longitudinal waves are waves where the particles oscillate parallel to the direction of energy transfer, while for transverse, it is perpendicular.
2. All longitudinal waves require a medium to transfer energy through as they are all mechanical waves, meanwhile transverse waves do not necessarily require a medium as not all are mechanical e.g. EM spec
3. Transverse waves can be polarised, longitudinal waves cannot

Question 18

Define reflection and what changes

Answer 18

Reflection occurs when a wave changes direction when it meets the boundary between two media and remains in the original medium.

Wavelength and frequency remains the same

Question 19

Define refraction and what changes

Answer 19

Refraction is when a wave changes direction as it changes speed

Wavelength changes since wave speed changes but frequency remains the same

Question 20

Define diffraction and what changes?

Answer 20

Diffraction is the spreading out of a wavefront through a gap or past an obstruction.

Frequency and wave length remain the same but amplitude changes.

Question 21

Define polarisation; what changes?

Answer 21

Polarisation is when the oscillations of a wave are restricted to be in one direction only (otherwise known as plane polarised; in one plane)

The wave’s oscillations are now in one plane only, the intensity of the wave also changes.